Method for producing recycled polyester resin, liquid colored resin composition used therefor, and molded article

Abstract

To provide a method for producing a regenerated polyester resin excellent in hue and productivity, and to provide a molded article excellent in productivity, free from variation between shots and contamination of a molding line, and excellent in transparency and appearance.SOLUTION: A method for producing a regenerated polyester resin, the method comprising all of steps [1] to [5] in this order, wherein polymerization of a polyester resin is performed simultaneously with pelletization in step [3] or decontamination in step [5], the method for producing a recycled polyester resin includes a step of adding a liquid coloring resin composition before or simultaneously with the step [3], wherein the liquid coloring resin composition contains a liquid dispersion medium (A), a dispersing agent (B), and a pigment (C), the liquid dispersion medium (A) has a viscosity at 25 °C. of 10,000 mPa·s or less and a decomposition initiation temperature of 250 °C. or higher, and the pigment (C) is at least one selected from the group consisting of a phthalocyanine-based pigment, an anthraquinone-based pigment, a cobalt-based pigment, and ultramarine.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled polyester resin, a liquid colored resin composition used therein, and a molded article. [Background technology]

[0002] Polyester resins are used in a variety of fields, including containers and films, due to their excellent transparency, dimensional stability, mechanical properties, heat resistance, and electrical properties. With growing environmental awareness in recent years, interest in plastic recycling has grown, and recycled polyethylene terephthalate (PET) resins are beginning to be used in PET bottles, food contact trays, and other products.

[0003] Known methods for recycling polyester resin include chemical recycling, in which recovered polyester molded bodies are chemically treated to convert them into raw materials for reuse, and mechanical recycling, in which recovered polyester molded bodies are crushed and washed to turn them into resin flakes, which are then treated at high temperatures to decontaminate contaminants remaining inside the resin, and the molecular weight that has decreased during the molding and recycling processes is polymerized to increase the molecular weight. While chemical recycling produces highly transparent recycled polyester resin, it requires large-scale facilities and high operating costs. Therefore, mechanical recycling has been widely considered. However, the recycled polyester resin produced by this method has the problem of turning yellow due to trace impurities remaining. Furthermore, the decontamination process to remove impurities and the crystallization process take time, resulting in low productivity.

[0004] To improve this hue, a method of adding a blue coloring material called a bluing agent is known. For example, Patent Document 1 describes a polyester container made of mechanically recycled polyester and a dye having a vaporization temperature of 230°C or less at 15 mbar. Patent Document 2 describes a method for producing a recycled polyester molded product using recycled polymers made of a molded polyester composition and a tinting agent, and cites oil-soluble dyes as examples of preferred tinting agents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-158785 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-182858 Summary of the Invention [Problem to be solved by the invention]

[0006] However, these methods have the problem that the color of the obtained recycled polyester resin is not sufficiently improved, and productivity is low. In addition, problems such as contamination of the molding line due to the colorant slipping down and poor dispersion of the colorant can occur, causing defects in the appearance of the molded product. Furthermore, when a dye is used as a bluing agent as in Patent Documents 1 and 2, there is a concern that the dye may leach out or migrate into the contents. For example, when contents are hot-filled into a PET bottle made of recycled polyester resin that has been blued with a dye, there is a concern that the dye may leach into the contents, or when food is heated using a tray made of recycled PET resin, the dye may migrate into the food.

[0007] Therefore, an object of the present invention is to provide a method for producing a recycled polyester resin that is excellent in hue and productivity, and to provide a molded article that is excellent in productivity, free from shot-to-shot variation and molding line contamination, and has excellent transparency and appearance by using the recycled polyester resin. Furthermore, the present invention aims to provide a recycled polyester resin and a molded article that, when used in beverage containers or the like, do not leach out a bluing agent into the contents or transfer odors to the contents. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention includes the following embodiments, but is not limited to the following. <1> A method for producing a recycled polyester resin, comprising the following steps [1] to [5] in this order, and polymerizing a polyester resin simultaneously with step [3] or step [5]: The method includes a step of adding a liquid colored resin composition before or simultaneously with the step [3], The liquid colored resin composition comprises a liquid dispersion medium (A), a dispersant (B), and a pigment (C), The liquid dispersion medium (A) has a viscosity of 10,000 mPa·s or less at 25°C and a decomposition temperature of 250°C or higher, The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. A method for producing recycled polyester resin. Process [1]: Crushing and washing the recovered polyester molded bodies to produce resin flakes Step [2]: Drying the resin flakes Step [3]: Pelletizing the dried resin flakes in an extruder Step [4]: ​​Crystallizing the pellets Step [5]: Decontamination of crystallized pellets <2> The pigment (C) is a phthalocyanine pigment. <1> A method for producing the recycled polyester resin described above. <3> The liquid dispersion medium (A) is at least one of an aliphatic polyester resin and a polyalkylene glycol resin. <1> or <2> A method for producing the recycled polyester resin described above. <4> The dispersant (B) is at least one of an acrylic resin and a surfactant. <1> ~ <3> A method for producing any one of the recycled polyester resins. <5> The content of the liquid colored resin composition is 0.005 to 1.0 parts by mass per 100 parts by mass of the dry resin flakes. <1> ~ <4> A method for producing any one of the recycled polyester resins. <6> <1> ~ <5> A liquid colored resin composition used in any one of the methods for producing recycled polyester resins. <7> <1> ~ <5> A molded article obtained by molding the recycled polyester resin produced by any of the methods described above. [Effects of the Invention]

[0009] The present invention provides a recycled polyester resin that is excellent in color and productivity, and also provides molded articles that are free from shot-to-shot variations and molding line contamination, and that are excellent in transparency and appearance. Furthermore, when used in beverage containers and the like, it is possible to provide a molded article that does not allow the bluing agent to leach out into the contents or transfer odors. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. Needless to say, other embodiments are also included in the scope of the present invention as long as they are consistent with the spirit of the present invention. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the range of the lower and upper limits. Here, "liquid" refers to being liquid at 25°C, and "CI" means color index. Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more. The numerical values ​​specified in this specification are values ​​determined by the methods disclosed in the embodiments or examples. In addition, in this specification, "simultaneously with the process" may refer to a step in the process, or a step performed sequentially or continuously, as long as it is within the process. For example, in the case of step [3]: a step of adding a liquid colored resin composition simultaneously with a step of pelletizing dried resin flakes in an extruder, the liquid colored resin composition may be added at any stage within the pelletizing step. In addition, the process of adding the liquid colored resin composition may be referred to as process [X], and the polyester resin polymerization process may be referred to as process [Y]. For example, process [3X] indicates that process [3] and process [X] are performed within the same process.

[0011] <<Manufacturing method for recycled polyester resin>> The present invention will be described in detail below. Recycled polyester resin is produced by crushing and washing the collected polyester moldings to produce resin flakes, drying the resin flakes, pelletizing them in an extruder, crystallizing the pellets, decontaminating the crystallized pellets, and polymerizing the molecular weight that was reduced during the molding and recycling processes to increase the molecular weight.

[0012] The method for producing a recycled polyester resin of the present invention comprises all of the following steps [1] to [5] in this order, and polymerizing the polyester resin simultaneously with step [3] or step [5], The method includes a step of adding a liquid colored resin composition before or simultaneously with the step [3]. The liquid colored resin composition contains a liquid dispersion medium (A), a dispersant (B), and a pigment (C), The liquid dispersion medium (A) has a viscosity of 10,000 mPa·s or less at 25°C and a decomposition temperature of 250°C or higher, The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. Process [1]: Crushing and washing the recovered polyester molded bodies to produce resin flakes Step [2]: Drying the resin flakes Step [3]: Pelletizing the dried resin flakes in an extruder Step [4]: ​​Crystallizing the pellets Step [5]: Decontamination of crystallized pellets

[0013] In this way, by adding the liquid colored resin composition of the present invention before or simultaneously with step [3], the colorant is uniformly dispersed in the recycled polyester resin. Therefore, compared to when a bluing colorant is added after the recycled polyester resin is made, i.e., after step [5], and a molded article is formed, contamination of the molding line due to the colorant slipping down and the occurrence of defective appearances in the molded article due to poor dispersion of the colorant can be suppressed. Furthermore, by using the liquid colored resin composition, excellent transparency and appearance can be achieved. Furthermore, when used for beverage containers, the recycled polyester resin can be used without leaching of coloring materials into the contents or transferring odors.

[0014] The polyester resin polymerization method may be liquid phase polymerization, in which the polymerization reaction proceeds at a temperature above the melting point while the polyester resin is in a liquid state, or solid phase polymerization, in which the polymerization proceeds in a solid state. For example, in the case of liquid phase polymerization, the polyester resin can be polymerized simultaneously with the process of pelletizing dried resin flakes in an extruder, while in the case of solid phase polymerization, the polyester resin can be polymerized simultaneously with the process of decontaminating crystallized pellets.

[0015] More specifically, in the case of solid-phase polymerization, for example, production method (a) is preferred in which polymerization of the polyester resin is carried out simultaneously with decontamination in step [5]. <Manufacturing method (a)> Step [1a]: A step of crushing and washing the recovered polyester molded body to produce resin flakes Step [2a]: Drying the resin flakes Step [X]: Adding a liquid colored resin composition Step [3a]: A step of pelletizing the dried resin flakes in an extruder Step [4a]: Crystallizing the pellets Step [5aY]: A step of polymerizing and decontaminating polyester resin using crystallized pellets It is preferable to carry out the steps in this order. Note that step [X] may be carried out before step [3a] or simultaneously with step [3a].

[0016] Furthermore, for example, in the case of liquid phase polymerization, production method (b) is preferred, in which polymerization of the polyester resin is carried out simultaneously with pelletization in step [3]. <Manufacturing method (b)> Step [1b]: A step of crushing and washing the recovered polyester molded body to produce resin flakes Step [2b]: Drying the resin flakes Step [X]: Adding a liquid colored resin composition Step [3bY]: Polymerizing and pelletizing polyester resin using dried resin flakes in an extruder Step [4b]: Crystallizing the pellets Step [5b]: Decontamination of crystallized pellets It is preferable to have the steps in this order. Note that step [X] may be carried out before step [3bY] or simultaneously with step [3bY].

[0017] (Process [1]) In step [1], the recovered polyester molded bodies are crushed and washed to produce resin flakes. Examples of polyester molded products recovered from the market include bottles, trays, packs, etc., which are formed from polyester resins by injection molding, vacuum molding, or blow molding. The recovered polyester molded products are crushed in a crusher, and then foreign matter such as labels and metals is removed. After that, the products are processed into flakes through washing, dehydration, and drying processes. As the crusher, a conventionally known device can be used, for example, a Z-Ace series crusher (manufactured by Horai Co., Ltd.).

[0018] (Process [2]) Step [2] is a step of drying the resin flakes obtained in step [1], and dried resin flakes are obtained. Drying the resin flakes can prevent a decrease in molecular weight due to hydrolysis during the subsequent extrusion process. The conditions for drying the resin flakes are not particularly limited, but they can be treated, for example, at 140 to 190°C for 3 to 6 hours.

[0019] (Process [3]) In step [3], the dried resin flakes are pelletized in an extruder to obtain pellets. The extruder used to pelletize the dried resin flakes is not particularly limited, and examples include a single-screw extruder and a twin-screw extruder. Since the viscosity of the polyester resin decreases little during extrusion, pelletization using a single-screw extruder is preferred. The temperature of the extruder can be set to, for example, 280 to 300°C to pelletize the dried resin flakes.

[0020] In addition, when the recycled polyester resin is produced by liquid phase polymerization, the polyester resin may be polymerized simultaneously with the pelletization in step [3]. For example, the polyester resin may be polymerized by treating it in an extruder at a treatment temperature of 280 to 300°C under vacuum for 30 minutes, and then pelletized.

[0021] Furthermore, the method for producing a recycled polyester resin of the present invention is characterized by comprising a step of adding a liquid colored resin composition before or simultaneously with step [3]. That is, in step [3], the dried resin flakes and the liquid colored resin composition may be mixed, followed by pelletization and polymerization of the polyester resin. Alternatively, the addition of the liquid colored resin composition, pelletization, and polymerization of the polyester resin may be carried out simultaneously. It is preferable to carry out the addition of the liquid colored resin composition, pelletization, and polymerization of the polyester resin simultaneously, as this reduces contamination of the production equipment.

[0022] (Process [X]) The manufacturing method of the present invention is characterized by comprising a step of adding a liquid colored resin composition before or simultaneously with the step [3] of pelletizing the dried resin flakes in an extruder. When the colored resin composition is added before pelletization, the colored resin composition and the dried resin flakes can be mixed and then charged into an extruder. There are no particular restrictions on the equipment used to mix the colored resin composition and the dried resin flakes, but for example, a Super Mixer (manufactured by Kawata Co., Ltd.) can be used.

[0023] When the liquid colored resin composition is added simultaneously with the pelletization, the dried resin flakes and the liquid colored resin composition can be separately charged into an extruder, mixed in the extruder, and pelletized. There are no particular restrictions on the method for adding the liquid colored resin composition, but for example, a tube pump (manufactured by Kawasaki Kikai Kogyo Co., Ltd.) can be used.

[0024] In this way, by including a liquid colored resin composition during the pelletizing step [3], the colorant is uniformly dispersed in the recycled polyester resin, and compared to the conventional method of adding a bluing agent to the recycled polyester resin after step [5] to form a molded product, contamination of the molding line due to the colorant slipping and the occurrence of defective appearance in the molded product due to poor dispersion of the colorant can be suppressed. Furthermore, compared to when a bluing agent is added to the recycled polyester resin, the colorant is uniformized, and therefore shot-to-shot variation in the hue of the molded product when molded using the recycled polyester resin can be reduced.

[0025] The amount of the liquid colored resin composition added is preferably 0.005 to 1.0 parts by mass per 100 parts by mass of dried resin flakes. Since shot-to-shot variability in the hue of the molded product is suppressed when molding using recycled polyester resin, the lower limit of the amount of the liquid colored resin composition added is more preferably 0.01 parts by mass, and since poor appearance such as flash does not occur in the appearance of the molded product, the upper limit of the amount of the liquid colored resin composition added is preferably 0.5 parts by mass. Since shot-to-shot variability and the appearance of the molded product can be achieved at the same time, the amount of the liquid colored resin composition added is even more preferably 0.01 to 0.25 parts by mass.

[0026] (Process [4]) In step [4], the obtained pellets are crystallized to obtain crystallized pellets. Crystallization of the pellets can prevent the pellets from adhering to each other in the subsequent decontamination step. The crystallization of the pellets can be carried out, for example, by heat treatment at 140 to 160°C for 4 to 6 hours.

[0027] (Process [5]) Step [5] is a step of decontaminating the crystallized pellets. Decontamination can remove contaminants remaining inside the resin. Crystallized pellets can be decontaminated, for example, by heat treatment at atmospheric pressure at 190 to 220°C for 20 to 24 hours.

[0028] Furthermore, when the recycled polyester resin is produced by solid-phase polymerization, the polyester resin may be polymerized simultaneously with the pelletization in step [5]. For example, by treating the polyester resin under vacuum at 190-220°C for 20-24 hours, removal of harmful substances such as acetaldehyde and polymerization of the polyester resin can be simultaneously achieved. When the recycled polyester resin is produced by liquid-phase polymerization, the reaction rate is fast, so the polymerization process time can be shortened compared to solid-phase polymerization. Furthermore, when the recycled polyester resin is produced by solid-phase polymerization, the processing time at 280-300°C is shortened, so a recycled polyester resin with less yellowing can be obtained compared to liquid-phase polymerization.

[0029] <<Recycled polyester moldings>> A polyester resin can usually be obtained by polymerizing a carboxylic acid component (a compound having a carboxyl group) and a hydroxyl component (a compound having a hydroxyl group).

[0030] The polyester molded products collected from the market are molded products containing polyester resin as a main component, and examples thereof include bottles, trays, packs, films, etc., which are formed from polyester resin by injection molding, vacuum molding, blow molding, or extrusion molding. Bottles are preferred as the collected polyester molded products because they are easy to separate and collect.

[0031] <<Liquid colored resin composition>> The liquid colored resin composition of the present invention comprises a liquid dispersion medium (A), a dispersant (B), and a pigment (C). The liquid dispersion medium (A) has a viscosity of 10,000 mPa·s or less at 25°C and a decomposition onset temperature of 250°C or higher. The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. The recycled polyester resin produced by the manufacturing method of the present invention using such a liquid colored resin composition has excellent hue, transparency, and productivity, and exhibits excellent appearance and color stability in molded products. Furthermore, the colorant does not leach or migrate into the contents, and odor transfer to the contents is minimal, making it suitable for use in beverage containers and the like.

[0032] <Liquid dispersion medium (A)> The liquid dispersion medium (A) used in the present invention will now be described. The liquid dispersion medium (A) serves as a dispersion medium for dispersing the pigment (C), and has a viscosity of 10,000 mPa·s or less at 25° C. From the viewpoints of dispersibility of the pigment (C) and supplyability when made into a liquid colored resin composition, the viscosity of the liquid dispersion medium (A) is preferably 10 to 7,000 mPa·s, and more preferably 20 to 5,000 mPa·s. The viscosity in this specification is a value measured using a B-type viscometer in accordance with JIS K7117-1.

[0033] The decomposition starting temperature of the liquid dispersion medium (A) is 250° C. or higher. In order to prevent the occurrence of poor appearance in the molded article and to achieve good mechanical properties such as impact strength, the decomposition starting temperature is preferably 260° C. or higher, and more preferably 270° C. or higher. There is no particular upper limit to the decomposition starting temperature, but from the viewpoint of the handleability of the liquid dispersion medium (A), it is preferably 320° C. or lower. The decomposition starting temperature in this specification is the temperature at which a 10% loss in weight occurs when the temperature is increased at a rate of 10°C / min using a Hitachi High-Tech Science "STA7200".

[0034] The freezing point of the liquid dispersion medium (A) is preferably -5°C or lower, more preferably -50°C to -10°C.

[0035] Examples of the liquid dispersion medium (A) include aliphatic polyester resins, polyalkylene glycol resins, polyether ester resins, aromatic polycarboxylic acid esters, etc. The liquid dispersion medium (A) is preferably at least one of an aliphatic polyester resin and a polyalkylene glycol resin, since there is little elution or migration into the contents and little effect on odor.

[0036] [Aliphatic polyester resin] The aliphatic polyester resin is a polyester resin obtained by reacting an aliphatic polycarboxylic acid with a polyhydric alcohol.

[0037] The aliphatic polycarboxylic acid constituting the aliphatic polyester resin is not particularly limited as long as it is an aliphatic carboxylic acid having two or more carboxyl groups, and examples thereof include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, tricarballylic acid, 1,3,6-hexatricarboxylic acid, 1,3,5-hexatricarboxylic acid, etc. These aliphatic carboxylic acids may be used alone or in combination of two or more.

[0038] The polyhydric alcohol constituting the aliphatic polyester resin is not particularly limited as long as it is an alcohol having two or more hydroxyl groups, and examples thereof include aliphatic glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and 1,12-octadecanediol, and polyalkylene glycols such as diethylene glycol and dipropylene glycol.

[0039] Specific examples of aliphatic polyester resins include Adeka Cizer PN-7160 (manufactured by Adeka Corporation, viscosity 150 mPa·s, freezing point −42°C, adipic acid polyester resin) and Adeka Cizer PN-5090 (manufactured by Adeka Corporation, viscosity 10,000 mPa·s, freezing point −10°C, adipic acid polyester resin).

[0040] [Polyalkylene glycol resin] Polyalkylene glycol resins are generally composed of alkylene glycols having repeating units with 1 to 6 carbon atoms, but various polyalkylene glycols can be used as long as their viscosity at 25°C is 10,000 mPa s or less. From the viewpoints of compatibility and water absorbency, polyalkylene glycol resins having repeating units with 2 to 4 carbon atoms are preferred.

[0041] Specific examples of polyalkylene glycol resins include polyethylene glycol, which has two carbon atoms in the repeating unit, polypropylene glycol, which has three carbon atoms in the repeating unit, and polybutylene glycol, which has four carbon atoms in the repeating unit.

[0042] Specific examples of polyalkylene glycol resins include PEG#300 (NOF Corporation, viscosity 70 mPa·s, polyethylene glycol) and Uniol D-1200 (NOF Corporation, viscosity 200 mPa·s, polypropylene glycol).

[0043] [Polyetherester resin] The polyether ester resin is obtained by esterifying the above-mentioned aliphatic polycarboxylic acid with the above-mentioned alkylene glycol.

[0044] Specific examples of polyetherester resins include Adeka Cizer RS-107 (manufactured by Adeka Corporation, viscosity 20 mPa·s, freezing point −47°C) and Adeka Cizer RS-700 (manufactured by Adeka Corporation, viscosity 30 mPa·s, freezing point −53°C).

[0045] [Aromatic polycarboxylic acid esters] The aromatic polycarboxylic acid ester is a polyester resin obtained by reacting an aromatic polycarboxylic acid with a polyhydric alcohol.

[0046] The aromatic polycarboxylic acid constituting the aromatic polycarboxylic acid ester is not particularly limited as long as it is an aromatic carboxylic acid having two or more carboxyl groups, and examples thereof include aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid.

[0047] The polyhydric alcohol constituting the aromatic polycarboxylic acid ester resin is not particularly limited as long as it is an alcohol having two or more hydroxyl groups, and examples thereof include aliphatic glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and 1,12-octadecanediol, and polyalkylene glycols such as diethylene glycol and dipropylene glycol.

[0048] Specific examples of aromatic polycarboxylic acid esters include Adeka Cizer UL-80 (manufactured by ADEKA Corporation, viscosity 450 mPa·s, pyromellitic acid alkyl ester) and Adeka Cizer UL-100 (manufactured by ADEKA Corporation, viscosity 176 mPa·s, pyromellitic acid alkyl ester).

[0049] <Dispersant (B)> The dispersant (B) interacts with the pigment (C) and functions to uniformly disperse the pigment (C) in the liquid dispersion medium (A). Examples of the dispersant (B) include acrylic resins and surfactants. From the viewpoint of dispersibility of the pigment (C), when the pigment (C) is an organic pigment such as a phthalocyanine pigment or an anthraquinone pigment, the dispersant (B) is preferably an acrylic resin, and when the pigment (C) is an inorganic pigment such as a cobalt pigment or ultramarine, the dispersant (B) is preferably a surfactant. By using such a dispersant (B), it is possible to produce a recycled polyester resin that has excellent appearance and moldability of the molded product.

[0050] The content of the dispersant (B) is preferably 0.5 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the pigment (C), because this improves the dispersibility of the pigment (C) and provides excellent suppression of the transparency, appearance, and shot-to-shot variation of the molded product.

[0051] The acrylic resin used as the dispersant (B) is a polymer containing (meth)acrylic monomer units, and examples thereof include (meth)acrylic resin and styrene-acrylic resin. The acrylic resin preferably has at least one polymer block consisting of (meth)acrylic monomer units. The weight-average molecular weight of the acrylic resin is preferably 500 to 20,000, more preferably 1,000 to 15,000, from the viewpoints of solubility in the liquid dispersion medium (A) and the physical properties of the thermoplastic resin (D). The weight average molecular weight in the present invention is a value measured by gel permeation chromatography (GPC method) (a measured value obtained using polystyrene as a standard substance and tetrahydrofuran as an eluent).

[0052] Examples of the (meth)acrylic monomer constituting the polymer include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and phenoxyethyl. (meth)acrylates such as (meth)acrylate, nonylphenoxyethyl (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and (meth)acrylic acid or esters thereof, such as mono(meth)acrylates having a (poly)alkylene glycol group, such as (poly)ethylene glycol, (poly)propylene glycol, and (poly)butylene glycol.

[0053] The styrene-acrylic resin is a copolymer of a styrene monomer and the (meth)acrylic monomer. Examples of the styrene monomer include styrene and α-methylstyrene. The styrene-acrylic resin is preferably a polymer having a styrene polymer block and a (meth)acrylic polymer block.

[0054] The acrylic resin in the present invention may have a functional group, and examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, an alkyl group, and an alkoxysilyl group.

[0055] Specific examples of acrylic resins include Alphon UP-1000 (manufactured by Toagosei Co., Ltd., weight average molecular weight 3,000, acrylic resin) and Alphon UP-2170 (manufactured by Toagosei Co., Ltd., weight average molecular weight 14,000, styrene-acrylic resin).

[0056] Surfactants (B) have hydrophilic and lipophilic groups in their molecules, and by strong adsorption to the interface of immiscible substances and molecular orientation, they work to reduce interfacial tension. Examples of surfactants include hydrogenated castor oil, metal soaps, and phosphate ester compounds. The use of these surfactants can improve the dispersibility of pigments (C), especially inorganic pigments.

[0057] The hydrogenated castor oil is a hardened castor oil obtained by adding hydrogen to the unsaturated bonds of castor oil, and is a triglyceride of 12-hydroxystearic acid. A specific example of hydrogenated castor oil is Kawastar CR (manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0058] The metal soap is a metal salt of a fatty acid, and examples of the fatty acid include long-chain fatty acids such as stearic acid, lauric acid, ricinoleic acid, octylic acid, montanic acid, and palmitic acid. The fatty acid may have a substituent such as a hydroxy group to enhance its adsorption to the pigment (C). Examples of the metal include lithium, magnesium, calcium, barium, and zinc. The metal soap is preferably magnesium stearate, and more preferably 12-hydroxy magnesium stearate, because of its good adsorption to the pigment (C). Specific examples of the metal soap include Sinaka Red SAK-MS-P (manufactured by San-Ace Co., Ltd., magnesium stearate) and MS-6 (manufactured by Nitto Kasei Kogyo Co., Ltd., magnesium stearate).

[0059] Examples of the phosphate ester compound include alkyl phosphates such as tributyl phosphate, trioctyl phosphate, tris(β-chloroethyl)phosphate, tris(β-chloropropyl)phosphate, and tris(dichloropropyl)phosphate; phenyl phosphates such as triphenyl phosphate, tricresyl phosphate, tris(i-properphenyl)phosphate, cresyl diphenyl phosphate, and octyl diphenyl phosphate; alkyl polyoxyethylene phosphates such as tributoxyethyl phosphate; alkylphenol polyoxyethylene phosphate esters; and their neutralized salts with sodium, potassium, ammonia, amine, or the like. These phosphate ester compounds may also have an acid value or an amine value. These phosphate ester compounds may be used alone or in combination of two or more. From the viewpoint of the dispersibility and sedimentation stability of the pigment (C), the phosphate ester compound is preferably an alkyl polyoxyethylene phosphate ester or alkylphenol polyoxyethylene phosphate ester having an acid value or an amine value.

[0060] Specific examples of the phosphate ester compound include ADEKA REASOAP PP-70 (manufactured by ADEKA Corporation, phosphate ester), DISPER BYK-102 (manufactured by BYK-Chemie, acid value 101 mgKOH / g), and DISPER BYK-145 (manufactured by BYK-Chemie, acid value 76 mgKOH / g, amine value 71 mgKOH / g).

[0061] The acid value of the dispersant (B) is preferably 180 mgKOH / g or less, and more preferably 140 mgKOH / g or less, from the viewpoints of the dispersibility of the pigment (C) and the physical properties of the recycled polyester resin.

[0062] The amine value of the dispersant (B) is preferably 180 mgKOH / g or less, more preferably 140 mgKOH / g or less, from the viewpoint of the physical properties of the recycled polyester resin of the pigment (C).

[0063] <Pigments> The liquid colored resin composition of the present invention contains a pigment (C) which is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. The inclusion of pigment (C) not only improves the yellowish hue of the recycled polyester resin and provides a bluing effect, but also promotes the crystallization of the recycled polyester resin, thereby shortening the time required for the crystallization process and improving productivity. Because of their high transparency and strong crystallization-promoting effect, organic pigments such as phthalocyanine pigments and anthraquinone pigments are preferred as pigment (C), with phthalocyanine pigments being particularly preferred due to their good hue.

[0064] Furthermore, pigment (C) is preferably a blue pigment. However, adding only a blue coloring material to a highly yellowish recycled polyester resin can result in a greenish hue. This green hue is undesirable, particularly for beverage bottles and food trays, as it is reminiscent of mold. Therefore, the pigment used in the present invention may contain other pigments in addition to pigment (C), and preferably contains at least one of organic pigments, such as quinacridone pigments and perylene pigments. The use of these pigments makes it possible to obtain a recycled polyester resin with a superior hue.

[0065] The blending amount of the pigment (C) is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, per 100 parts by mass of the liquid dispersion medium (A), in order to improve the dispersibility of the pigment (C) and the appearance of the molded product.

[0066] From the viewpoint of pigment dispersibility and the appearance of the recycled polyester resin, the total blend amount of pigment (C) and other pigments is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the liquid dispersion medium (A). When pigment (C) and other pigments are contained, the blend ratio of the other pigments is preferably 10 to 200 parts by mass, more preferably 50 to 120 parts by mass, per 100 parts by mass of pigment (C). By blending in the above amounts, a recycled polyester resin with good hue can be obtained.

[0067] Pigment The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. Examples of phthalocyanine pigments include CI Pigment Blue 15, Pigment Blue 15:1, and Pigment Blue 15:3. Examples of anthraquinone pigments include Pigment Blue 60. An example of a cobalt-based pigment is Pigment Blue 28. Examples of ultramarine include Pigment Blue 29 and Pigment Violet 15.

[0068] Specific examples of phthalocyanine pigments include FASTOGEN BLUE AR-7E (manufactured by DIC Corporation, Pigment Blue 15), FASTOGEN BLUE 5050AE (manufactured by DIC Corporation, Pigment Blue 15:1), and FASTOGEN BLUE PA5380 (manufactured by DIC Corporation, Pigment Blue 15:3). Specific examples of anthraquinone pigments include LIONOGEN BLUE R (Pigment Blue 60, manufactured by Toyo Color Co., Ltd.). Examples of cobalt pigments include 42-255A (manufactured by TOMATEC Corporation, Pigment Blue 28). Examples of ultramarine include Ultramarine No. 1500 (manufactured by Daiichi Kasei Co., Ltd., Pigment Blue 29) and Premier VU (manufactured by Tetsutani Co., Ltd., Pigment Violet 15).

[0069] [Other pigments] The other pigment is a pigment other than the pigment (C) and can be used without limitation according to the desired hue, but is preferably at least one of a quinacridone pigment and a perylene pigment. Examples of quinacridone pigments include Pigment Violet 19, Pigment Red 122, Pigment Red 202, and Pigment Red 209. Examples of perylene pigments include Pigment Red 178, Pigment Red 179, and Pigment Red 149.

[0070] Specific examples of quinacridone pigments include FASTOGEN SUPER RED 500RS (manufactured by DIC Corporation, Pigment Violet 19), FASTOGEN SUPER MAGENTA R (manufactured by DIC Corporation, Pigment Red 122), Cinquasia Magenta K4535FP (manufactured by Sun Chemical Co., Ltd., Pigment Red 202), and FASTOGEN SUPER RED 209 228-6736 (manufactured by DIC Corporation, Pigment Red 209). Specific examples of perylenes include Paliogen Red K3911 (manufactured by Sun Chemical Co., Ltd., Pigment Red 178), Paliogen Red K 4180 (manufactured by Sun Chemical Co., Ltd., Pigment Red 179), and Paliogen Red K 3580 (manufactured by Sun Chemical Co., Ltd., Pigment Red 149).

[0071] <Other additives> The liquid colored resin composition of the present invention may contain any other polymer, antistatic agent, antifoaming agent, matting agent, fluorescent brightener, stabilizer, antioxidant, viscosity modifier, and other additives.

[0072] <Method for producing liquid colored resin composition> The method for producing the liquid colored resin composition of the present invention is not particularly limited, and for example, the liquid dispersion medium (A), dispersant (B), pigment (C), and, if necessary, other additives are added, mixed in a Henschel mixer, tumbler, disperser, or the like, and dispersed using a Silverson mixer (manufactured by Silverson) or the like, to obtain a liquid colored resin composition. In addition to the above, any other dispersing device can be used, such as a kneader, roll mill, ball mill, or sand mill. It is preferable to use a bead mill, Silverson mixer, or roll mill because they are easy to mold and have excellent dispersibility.

[0073] <Molded body> The molded article is obtained by molding the recycled polyester resin produced by the production method of the present invention. The molded article of the present invention has excellent productivity, is free from shot-to-shot variations and molding line contamination, and has excellent transparency and appearance, and therefore can be used in a variety of applications. In particular, even when used in food contact containers such as beverage containers, trays, cups, and films, recycled polyester resins and molded articles can be produced that do not leach out bluing agents into the contents or transfer odors. At the time of filing, it was impossible or practical to directly identify the recycled polyester resin and molded articles by their structure or properties.

[0074] The molding method used to mold recycled polyester resin to obtain a molded body is not particularly limited, and examples include blow molding used to mold bottles, extrusion molding used to mold sheets and films, vacuum molding used to mold trays, and injection molding used to mold cups. [Example]

[0075] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. In the examples, parts and % represent parts by mass and % by mass, respectively, unless otherwise specified. Note that blank spaces in the tables indicate that no ingredients were blended.

[0076] The materials used in the examples and comparative examples are shown below. <Liquid dispersion medium (A) etc.> A-1: Adeka Cizer PN-7160 (ADEKA Corporation, aliphatic polyester resin, viscosity at 25°C: 150 mPa·s, decomposition temperature: 278°C) A-2: Uniol D-1200 (NOF Corporation, polyalkylene glycol resin, viscosity at 25°C: 200 mPa·s, decomposition temperature: 276°C) A-3: Adeka Cizer RS-700 (ADEKA Corporation, polyetherester resin, viscosity at 25°C: 30 mPa·s, decomposition temperature: 300°C) A'-4: BIOCIZER (Riken Vitamin Co., Ltd., acetylated monoglyceride, viscosity at 25°C: 30 mPa·s, decomposition temperature: 228°C)

[0077] <Dispersant (B)> B-1: ARUFON UP-1000 (Toagosei, acrylic resin) B-2: Kawastar CR (Kawaken Fine Chemicals Co., Ltd., surfactant: hydrogenated castor oil) B-3: MS-6 (manufactured by Nitto Kasei Kogyo Co., Ltd., surfactant: magnesium 12-hydroxystearate)

[0078] <Pigment (C), etc.> C-1: FASTOGEN BLUE 5050AE (DIC, phthalocyanine pigment, pigment blue 15:1) C-2: Corimax Blue A3R (ZEYACHEM, anthraquinone pigment, Pigment Blue 60) C-3: Ultramarine No. 1500 (Daiichi Kasei Co., Ltd., ultramarine, Pigment Blue 29) C-4: 42-214A (TOMATEC, cobalt pigment, Pigment Blue 28) C'-5: Paliogen Red K3911 (Sun Chemical, perylene pigment, Pigment Red 178) C'-6: Macrolex Violet B (Bayer, anthraquinone dye, Solvent Violet 13)

[0079] <Method of manufacturing recycled polyester resin> [Reference example (a); Manufacturing method (a)] Recycled PET resin (a) (IV: 0.80 dL / g) was obtained through the following steps [1a] to [5aY]. Step [1a]: PET resin (Mitsui Pet SA135, manufactured by Mitsui Chemicals, Inc., IV: 0.84 dL / g) was blown into a PET bottle using an injection blow molding machine (manufactured by Nissei ASB Machinery Co., Ltd.). The resulting PET bottle was then crushed into flakes using a crusher (manufactured by Nippon Seam Co., Ltd.), washed with water, and dehydrated to obtain resin flakes (IV: 0.79 dL / g). Step [2a]: The resin flakes were dried in a dryer (manufactured by Matsui Manufacturing Co., Ltd.) at atmospheric pressure at 160°C for 4 hours. Step [3a]: The dried resin flakes were pelletized at 280°C using a single-screw extruder (manufactured by Thermoplastics Co., Ltd.) (IV: 0.72 dL / g). Step [4a]: The obtained pellets were crystallized in a dryer (manufactured by Matsui Manufacturing Co., Ltd.) at atmospheric pressure and 140°C. Step [5aY]: The crystallized pellets were treated in a vacuum oven (manufactured by Yamato Scientific Co., Ltd.) at 205°C for 24 hours under vacuum conditions to carry out solid-state polymerization and decontamination, thereby obtaining a recycled polyester resin (a) (IV: 0.80 dL / g). The increase in molecular weight of the recycled polyester resin can be confirmed by the increase in intrinsic viscosity (IV).

[0080] [Reference example (b); Manufacturing method (b)] Recycled PET resin (b) (IV: 0.80 dL / g) was obtained through the following steps [1b] to [5b]. Step [1b]: PET resin (Mitsui Pet SA135, manufactured by Mitsui Chemicals, Inc., IV: 0.84 dL / g) was blow-molded using an injection blow molding machine (manufactured by Nissei ASB Machinery Co., Ltd.) to obtain a PET bottle. The PET bottle was then crushed into flakes using a crusher (manufactured by Nippon Seam Co., Ltd.), washed with water, and dehydrated to obtain resin flakes (IV: 0.79 dL / g). Step [2b]: The resin flakes were dried in a dryer (manufactured by Matsui Manufacturing Co., Ltd.) at atmospheric pressure at 160°C for 4 hours. Step [3bY]: The dried resin flakes were subjected to liquid phase polymerization by treating them in a LSP liquid phase polymerization apparatus (manufactured by ACERETECH) at 300°C under vacuum for 30 minutes, and then pelletized. Step [4b]: The obtained pellets were crystallized in a dryer (manufactured by Matsui Manufacturing Co., Ltd.) at atmospheric pressure and 140°C. Step [5b]: The crystallized pellets were decontaminated by treating them in a vacuum oven (manufactured by Yamato Scientific Co., Ltd.) at atmospheric pressure at 205°C for 24 hours to obtain a recycled polyester resin (b) (IV: 0.80 dL / g). The increase in molecular weight of the recycled polyester resin can be confirmed by the increase in intrinsic viscosity (IV).

[0081] [Example 1] <Production of Liquid Colored Resin Composition> 100 parts by mass of liquid dispersion medium (A-1), 0.025 parts by mass of dispersant (B-1), and 0.25 parts by mass of pigment (C-1) were mixed and dispersed in a bead mill to obtain a liquid colored resin composition. <Production of recycled polyester resin> Before the step [3a] of Reference Example (a), 100 parts by mass of dried resin flakes and 0.1 parts by mass of a liquid colored resin composition were mixed to obtain a mixture. This mixture was pelletized using a single-screw extruder (manufactured by Thermoplastics Corporation). The same manufacturing method as Reference Example (a) was used to obtain recycled polyester resin 1. That is, the liquid colored resin composition was added before the step [3], and the polyester resin polymerization step was carried out simultaneously with the step [5].

[0082] [Example 2] <Production of Liquid Colored Resin Composition> 100 parts by mass of liquid dispersion medium (A-1), 0.025 parts by mass of dispersant (B-1), and 0.25 parts by mass of pigment (C-1) were mixed and dispersed in a bead mill to obtain a liquid colored resin composition. <Production of recycled polyester resin> Recycled polyester resin 2 was obtained in the same manner as in Reference Example (a), except that in step [3a] of Reference Example (a), 100 parts by mass of dried resin flakes and 0.1 parts by mass of liquid colored resin composition were each supplied separately and pelletized using a single-screw extruder (manufactured by Thermoplastics Corporation). That is, the addition of the liquid colored resin composition was carried out simultaneously with the step [3], and the polymerization step of the polyester resin was carried out simultaneously with the step [5].

[0083] [Examples 3 to 17, Comparative Examples 1 and 2] <Production of Liquid Colored Resin Composition> Liquid colored resin compositions were produced in the same manner as the liquid colored resin composition of Example 2, except that the materials and blending amounts (parts by mass) were changed to those shown in Tables 1 and 2, respectively. <Production of recycled polyester resin> Recycled polyester resins 3 to 17 and 19 to 21 were obtained in the same manner as in Example 2, except that the type or blending amount (parts by mass) of the liquid colored resin composition used was changed.

[0084] [Example 18] <Production of Liquid Colored Resin Composition> 100 parts by mass of liquid dispersion medium (A-1), 0.025 parts by mass of dispersant (B-1), and 0.25 parts by mass of pigment (C-1) were mixed and dispersed in a bead mill to obtain a liquid colored resin composition. <Production of recycled polyester resin> In step [3bY] of Reference Example (b), 100 parts by mass of dried resin flakes and 0.1 parts by mass of liquid colored resin composition (x-1) were each supplied separately, and subjected to liquid phase polymerization by treating at 300°C under vacuum for 30 minutes using an LSP liquid phase polymerization apparatus (manufactured by ACERETECH), and then pelletized to obtain recycled polyester resin 18. That is, the addition of the liquid colored resin composition was carried out simultaneously with the step [3], and the polymerization step of the polyester resin was carried out simultaneously with the step [3].

[0085] <Comparative Example 3> <Production of Liquid Colored Resin Composition> 100 parts by mass of liquid dispersion medium (A-1), 0.025 parts by mass of dispersant (B-1), and 0.25 parts by mass of pigment (C-1) were mixed and dispersed in a bead mill to obtain a liquid colored resin composition. <Production of recycled polyester resin> 0.1 parts by mass of the liquid colored resin composition was mixed with 100 parts by mass of the recycled polyester resin (a) obtained in the step [5] of Reference Example (a) to obtain a recycled polyester resin. That is, the liquid colored resin composition was added after step [5], and the polyester resin polymerization step was carried out simultaneously with step [5].

[0086] <Evaluation of recycled polyester resin> The recycled polyester resin of the present invention was evaluated by the following methods, and the results are shown in Tables 1 and 2. The results of the recycled polyester resin (a) obtained by the production method (a) without adding the liquid colored resin composition were described as Reference Example 1. The recycled polyester resin (b) obtained by the production method (b) also showed similar results.

[0087] <Productivity> During process [4] for the production of each recycled polyester resin, samples were taken every 10 minutes during the drying time, and the crystallization temperature of the pellets was measured using a DSC6200 (Seiko Instruments Inc.) at a temperature range of 40-300°C and a heating rate of 10°C / min. The time Tc (minutes) from when the crystallization temperature could no longer be measured until crystallization was complete was evaluated according to the following criteria. The shorter the time until the crystallization temperature could no longer be measured, the higher the productivity of the recycled polyester resin. [Evaluation criteria] +++: Tc<90, very good ++:90≦Tc<110, good +: 110≦Tc<120, practical NG: Tc≧120, not practical

[0088] <Dispersibility> The recycled polyester resin was used to make 50 plates measuring 150mm x 130mm x 2.0mm using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., injection pressure 100t). The surfaces of five randomly selected plates were observed, and the number of plates with visible black spots due to aggregation of coloring material was counted and evaluated according to the following criteria. [Evaluation criteria] +++: No black spots on any of the five plates, very good ++: One plate has visible black spots, good +: Two plates that can be used to check black spots NG: Three or more plates have visible black spots. Not suitable for practical use.

[0089] <Line contamination> After preparing the dispersibility evaluation plate, the molding machine hopper and the mold were washed with a cloth, and the degree of adhesion of the liquid colored resin composition and coloring material to the cloth was evaluated according to the following criteria. [Evaluation criteria] +++: No adhesion of the liquid colored resin composition or coloring material to the cloth, very good ++: Adhesion of the liquid colored resin composition and coloring material to the waste cloth can be confirmed slightly, good NG: Adhesion of the liquid colored resin composition and coloring material to the cloth is clearly visible, not suitable for practical use

[0090] <Hue> The obtained recycled polyester resin was used to prepare a plate measuring 87 mm x 50 mm x 1.5 mm using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., injection pressure 60 t). The transparency of the plate was evaluated using a spectrophotometer 36dG (manufactured by Komica Minolta Co., Ltd.). * value, b * The values ​​were measured and evaluated according to the following criteria. [Evaluation criteria] +++:b * Value ≦ 12 and a * Value ≥ -1.5, very good ++:b * Value ≦ 12 and -2.5 ≦ a * Value <-1.5, good +:b * Value ≦ 12 and a * Value < -2.5, usable NG:b * Value > 12 and a * Value < -2.5, not practical

[0091] <Transparency> The L of the plate used for hue evaluation was measured using a spectrophotometer 36dG (manufactured by Komica Minolta). * The values ​​were measured and evaluated according to the following criteria. [Evaluation criteria] +++:L * Value ≥ 89, very good ++:88≦L* Value < 89, good +:87≦L * Value < 88, usable NG:L * Value < 87, not practical

[0092] <Evaluation of beverage bottles, etc.> When using the molded article in a beverage bottle, etc., the elution property and odor were evaluated by the following methods. When the evaluation of elution property or odor is NG for use in a beverage bottle, etc., it can be said that the product is not suitable for practical use. <Dissolution> The plate used for hue evaluation was cut into pieces measuring 22 mm x 18 mm x 1.5 mm. Eight cut test pieces were immersed in 30 mL of 99.5% ethanol and left to stand in a water bath at 50°C for 7 days. The hue of the ethanol after removing the test pieces was evaluated visually, and the absorption spectrum was measured using a UV-3150 ultraviolet-visible-near-infrared spectrophotometer (Shimadzu Corporation) and evaluated according to the following criteria. [Evaluation criteria] +++: absorbance ε≦0.01 at 380-770 nm, very good ++: Absorbance at 380-770nm is 0.01<ε≦0.02, good +: Absorbance at 380-770nm is 0.02<ε≦0.03, practical use possible NG: absorbance ε>0.03 in the range of 380-770 nm, not practical

[0093] <Odor> 300 mL of mineral water and one of the plates used in the hue evaluation were placed in a 450 mL mayonnaise jar, and the jar was left to stand in a 40°C oven for 1 hour before being vigorously opened. The plate was then removed, and five panelists checked the odor of the mineral water and rated it according to the following criteria. [Evaluation criteria] +++: 0 panelists noticed an odor, very good ++: One panelist noticed an odor, good +: Two panelists noticed an odor, practical NG: Three or more panelists detected an odor, not suitable for practical use

[0094] [Table 1]

[0095] [Table 2]

[0096] As shown in Tables 1 and 2, the manufacturing method of the present invention produces recycled polyester resins with excellent hue and productivity, and it has been confirmed that by using this recycled polyester resin, molded articles with excellent transparency and appearance can be obtained without shot-to-shot variation or line contamination. Furthermore, it has been confirmed that recycled polyester resins and molded articles can be produced that do not leach colorants into the contents or transfer odors, making them suitable for use in beverage containers and the like.

Claims

1. A method for producing a recycled polyester resin, comprising the following steps [1] to [5] in this order, and polymerizing a polyester resin simultaneously with step [3] or step [5]: The method includes a step of adding a liquid colored resin composition before or simultaneously with the step [3], The liquid colored resin composition contains a liquid dispersion medium (A), a dispersant (B), and a pigment (C), the liquid dispersion medium (A) has a viscosity at 25°C of 10,000 mPa s or less and a decomposition initiation temperature of 250°C or higher; The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine. A method for producing recycled polyester resin. Step [1]: Crushing and washing the recovered polyester molded body to produce resin flakes Step [2]: Drying the resin flakes Step [3]: Pelletizing the dried resin flakes using an extruder Step [4]: ​​Crystallizing the pellets Step [5]: Decontamination of crystallized pellets

2. 2. The method for producing a recycled polyester resin according to claim 1, wherein the pigment (C) is a phthalocyanine pigment.

3. 2. The method for producing a recycled polyester resin according to claim 1, wherein the liquid dispersion medium (A) is at least one of an aliphatic polyester resin and a polyalkylene glycol resin.

4. The method for producing a recycled polyester resin according to claim 1, wherein the dispersant (B) is at least one of an acrylic resin and a surfactant.

5. The method for producing a recycled polyester resin according to claim 1, wherein the content of the liquid colored resin composition is 0.005 to 1.0 parts by mass per 100 parts by mass of the dry resin flakes.

6. A liquid colored resin composition used in the method for producing the recycled polyester resin according to any one of claims 1 to 5.

7. A molded article obtained by molding the recycled polyester resin produced by the method according to any one of claims 1 to 5.

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