Method for producing recycled polyester resin, liquid colored resin composition used therein, and molded product

Abstract

To provide a method for producing a recycled polyester resin excellent in hue and productivity, and to provide a molded product excellent in productivity, free from shot-to-shot variation and molding line contamination, and excellent in transparency and appearance. [Solution] The problem is solved by a method for producing a recycled polyester resin, which comprises all of steps [1] to [5] in the stated order, and which polymerizes the polyester resin simultaneously with the pelletization in step [3] or the decontamination in step [5], and which further comprises a step of adding a liquid colored resin composition before or simultaneously with step [3], wherein the liquid colored resin composition contains a liquid dispersion medium (A), a dispersant (B), and a pigment (C), wherein the liquid dispersion medium (A) has a viscosity at 25°C of 10,000 mPa s or less and a decomposition onset temperature of 250°C or higher, and the pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine.

Description

[Technical field]

[0001] The present invention relates to a method for producing a 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, such as containers and films, due to their excellent transparency, dimensional stability, mechanical properties, heat resistance, and electrical properties. With the recent increase in environmental awareness, interest in plastic recycling has been growing, and recycled polyethylene terephthalate (PET) resins are beginning to be used in PET bottles, food contact trays, etc.

[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 and then reused; 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 mechanical recycling, in which the molecular weight that has decreased during the molding and recycling processes is polymerized to increase the molecular weight. Chemical recycling produces highly transparent recycled polyester resin, but the equipment required is large-scale and the operating costs are high. For this reason, mechanical recycling has been widely considered, but the recycled polyester resin produced by this method has the problem of turning yellow due to trace amounts of remaining impurities. In addition, the decontamination process to remove impurities and the crystallization process take time, resulting in low productivity.

[0004] In order 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 a recycled polymer made of a molded polyester composition and a tinting agent, and lists an oil-soluble dye as a preferred tinting agent. [Prior art documents] [Patent documents]

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

[0006] However, these methods have problems such as insufficient improvement in the hue of the obtained recycled polyester resin and low productivity. In addition, problems such as contamination of the molding line due to the colorant slipping off and poor dispersion of the colorant can occur, resulting in defective 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 transfer to 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, and when food is heated using a tray made of recycled PET resin, the dye may transfer to the food.

[0007] Therefore, an object of the present invention is to provide a method for producing a recycled polyester resin having excellent hue and productivity, and to provide a molded product using the recycled polyester resin, which has excellent productivity, is free from shot-to-shot variation and molding line contamination, and has excellent transparency and appearance. Furthermore, the present invention aims to provide a recycled polyester resin and a molded article thereof which, when used in beverage containers or the like, does not cause the elution of a bluing agent into the contents or the transfer of odors thereto. [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. The embodiments of the present invention are 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 carrying out polymerization of 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 cleaning the recovered polyester molded bodies to produce resin flakes. Step [2]: Drying the resin flakes Step [3]: The dried resin flakes are pelletized using an extruder. Step [4]: ​​Crystallizing the pellets Step [5]: Decontamination of the 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 the recycled polyester resin according to any one of claims 1 to 4. <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 the recycled polyester resin according to any one of claims 1 to 4. <6> <1> ~ <5> A liquid colored resin composition for use in any one of the methods for producing a recycled polyester resin. <7> <1> ~ <5> A molded article obtained by molding the recycled polyester resin produced by any one of the methods described above. Effect of the Invention

[0009] According to the present invention, a recycled polyester resin having excellent color and productivity can be obtained. In addition, a molded product having excellent transparency and appearance can be obtained without shot-to-shot variation or molding line contamination. Furthermore, when used in beverage containers and the like, it is possible to provide a molded article that is free from the elution of the bluing agent into the contents and the transfer of odors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 gist of the present invention. In addition, in this specification, a numerical range specified using "~" includes the numerical values ​​before and after "~" as the range of the lower and upper limits. Here, "liquid" refers to being liquid at 25°C, and "CI" stands for Color Index. Unless otherwise noted, the various components appearing in this specification may be used independently as a single type or as a mixture of two or more types. 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 mean, as long as it is within the process, an intermediate stage of the process, or a sequential or continuous process. For example, in the case of step [3]: a process of adding a liquid colored resin composition simultaneously with a process of pelletizing dried resin flakes using an extruder, it is sufficient that the liquid colored resin composition is added at any stage within the pelletizing process. In addition, the process of adding the liquid colored resin composition is sometimes referred to as process [X], and the process of polymerizing the polyester resin is sometimes referred to as process [Y]. For example, process [3X] indicates that process [3] and process [X] are carried out within the same process.

[0011] <Production method of 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 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 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 cleaning the recovered polyester molded bodies to produce resin flakes. Step [2]: Drying the resin flakes Step [3]: The dried resin flakes are pelletized using an extruder. Step [4]: ​​Crystallizing the pellets Step [5]: Decontamination of the crystallized pellets

[0013] In this way, by adding the liquid colored resin composition of the present invention before or at the same time as step [3], the colorant is uniformly dispersed in the recycled polyester resin. Therefore, compared to the case where a bluing colorant is added after the recycled polyester resin is made, i.e., after step [5], to form a molded product, it is possible to suppress contamination of the molding line due to the colorant slipping off and the occurrence of defective appearance parts in the molded product due to poor dispersion of the colorant. In addition, the liquid colored resin composition has excellent transparency and appearance. Furthermore, when used for beverage containers, the recycled polyester resin does not leach coloring materials into the contents or transfer odors.

[0014] The polyester resin polymerization method may be liquid phase polymerization in which the polymerization reaction proceeds at a temperature equal to or higher than the melting point of the polyester resin 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 the dried resin flakes in an extruder, and in the case of solid phase polymerization, the polyester resin can be polymerized simultaneously with the process of decontaminating the crystallized pellets.

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

[0016] In addition, for example, in the case of liquid phase polymerization, a production method (b) is preferred in which polymerization of the polyester resin is carried out simultaneously with the pelletization in the step [3]. <Manufacturing method (b)> Step [1b]: Crushing and washing the recovered polyester molded bodies 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 the 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, washed, and turned into resin flakes. Examples of polyester molded products collected from the market include bottles, trays, packs, etc., which are formed from polyester resin by injection molding, vacuum molding, blow molding, etc. The collected polyester molded products are crushed by a crusher, and then foreign matter such as labels and metals are removed, followed by washing, dehydration, and drying processes to be processed into flakes. As the pulverizer, a conventionally known device can be used, for example, a Z-Ace series pulverizer (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. By drying the resin flakes, it is possible to suppress 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 for pelletizing the dried resin flakes is not particularly limited, and examples thereof include a single-screw extruder and a twin-screw extruder. Since the viscosity of the polyester resin is not significantly reduced during extrusion, it is preferable to pelletize the dried resin flakes using a single-screw extruder. The temperature of the extruder is, for example, 280 to 300°C, at which the dried resin flakes can be pelletized.

[0020] In addition, when the manufacturing method of the recycled polyester resin is liquid phase polymerization, the polyester resin may be polymerized simultaneously with the pelletization in step [3]. In this case, for example, the polyester resin can be polymerized by treating 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 including 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, and then pelletized and polymerized into a polyester resin. Alternatively, the addition of the liquid colored resin composition, pelletization, and polymerization of the polyester resin may be performed simultaneously. It is preferable to simultaneously add the liquid colored resin composition, pelletize, and polymerize the polyester resin, since 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 of pelletizing the dried resin flakes in an extruder in step [3]. When adding before pelletization, the liquid colored resin composition and the dry resin flakes can be mixed and fed into an extruder. There is no particular restriction on the equipment used to mix the liquid colored resin composition and the dry 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 at the same time as pelletization, the dry resin flakes and the liquid colored resin composition can be separately charged into an extruder, mixed in the extruder, and pelletized. There is no particular restriction on the method of 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 in step [3], the coloring material 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, it is possible to suppress contamination of the molding line due to the coloring material slipping off and the occurrence of defective parts in the molded product due to poor dispersion of the coloring material. Also, compared to the case of adding a bluing agent to the recycled polyester resin, the coloring material is made uniform, so that the 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 relative to 100 parts by mass of the dried resin flakes. The lower limit of the amount of the liquid colored resin composition added is more preferably 0.01 parts by mass because the shot-to-shot variation in the hue of the molded product is suppressed when molding using the recycled polyester resin, and the upper limit of the amount of the liquid colored resin composition added is preferably 0.5 parts by mass because the appearance of the molded product does not suffer from flash or other defects. The amount of the liquid colored resin composition added is more preferably 0.01 to 0.25 parts by mass because the shot-to-shot variation and the appearance of the molded product can be compatible.

[0026] (Process [4]) The step [4] is a step of crystallizing the obtained pellets, thereby obtaining crystallized pellets. By crystallizing the pellets, it is possible to prevent the pellets from sticking to each other in the subsequent decontamination process. The crystallization of the pellets is carried out, for example, by heat treatment at 140 to 160° C. for 4 to 6 hours.

[0027] (Process [5]) Step [5] is the process 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] In addition, when the method for producing the recycled polyester resin is solid-phase polymerization, the polyester resin may be polymerized simultaneously with the pelletization in step [5]. In this case, for example, by treating under vacuum at 190 to 220°C for 20 to 24 hours, it is possible to simultaneously remove harmful substances such as acetaldehyde and polymerize the polyester resin. In the case of liquid-phase polymerization, the reaction rate is fast, so the polymerization process time can be shortened compared to solid-phase polymerization. In addition, in the case of solid-phase polymerization, the time required for processing at 280 to 300°C is shortened, so a recycled polyester resin with less yellowness 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] Polyester molded products collected from the market are molded products containing polyester resin as a main component, and examples of such products include bottles, trays, packs, films, etc., which are molded from polyester resin by injection molding, vacuum molding, blow molding, extrusion molding, etc. Bottles are preferred as the recycled 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 includes 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 start temperature of 250°C or more, and 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 production method of the present invention using such a liquid colored resin composition has excellent hue, high transparency and productivity, and is excellent in appearance and color development stability of the molded product. Furthermore, since the coloring material does not dissolve or migrate into the contents and there is little odor transfer to the contents, it can be suitably used for 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 5000 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. Since the molded article does not have poor appearance and has 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 onset 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, and 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 polyvalent carboxylic acid esters, etc. The liquid dispersion medium (A) is preferably at least one of aliphatic polyester resins and polyalkylene glycol resins, since it is less likely to dissolve or migrate into the contents and has less 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 polyvalent carboxylic 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 a repeating unit 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 a repeating unit with 2 to 4 carbon atoms are preferred.

[0041] Specific examples of polyalkylene glycol resins include polyethylene glycol, the repeating unit of which has 2 carbon atoms, polypropylene glycol, the repeating unit of which has 3 carbon atoms, and polybutylene glycol, the repeating unit of which has 4 carbon atoms.

[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 and 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 polyvalent carboxylate 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), Adeka Cizer UL-100 (manufactured by ADEKA Corporation, viscosity 176 mPa·s, pyromellitic acid alkyl ester), and the like.

[0049] <Dispersant (B)> The dispersant (B) interacts with the pigment (C) and disperses the pigment (C) uniformly 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), a recycled polyester resin having excellent appearance and moldability of the molded product can be produced.

[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, relative to 100 parts by mass of the pigment (C), because this improves the dispersibility of the pigment (C) and provides excellent transparency, appearance, and suppression of shot-to-shot variation of the molded product.

[0051] The acrylic resin used as the dispersant (B) is a polymer containing a (meth)acrylic monomer unit, and examples thereof include a (meth)acrylic resin and a styrene-acrylic resin. The acrylic resin preferably has at least one polymer block consisting of a (meth)acrylic monomer unit. 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 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 above 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 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 Arfon UP-1000 (manufactured by Toa Gosei Co., Ltd., weight average molecular weight 3,000, acrylic resin) and Arfon UP-2170 (manufactured by Toa Gosei Co., Ltd., weight average molecular weight 14,000, styrene-acrylic resin).

[0056] Surfactants (B) have hydrophilic and lipophilic groups in their molecules, and they work to reduce interfacial tension by strong adsorption to the interface of immiscible substances and by molecular orientation. Examples of surfactants include hydrogenated castor oil, metal soaps, and phosphate ester compounds. The use of these surfactants can increase 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 the 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 hydroxyl group to enhance the 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), MS-6 (manufactured by Nitto Kasei Co., Ltd., magnesium stearate), and the like.

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

[0060] Specific examples of phosphate ester compounds include ADEKA REASOAP PP-70 (manufactured by ADEKA Corporation, phosphate ester), Disper BYK-102 (manufactured by BYK-Chemie, acid value 101 mg KOH / g), and Disper BYK-145 (manufactured by BYK-Chemie, acid value 76 mg KOH / g, amine value 71 mg KOH / 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, and 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 at least one pigment (C) selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine blue. The inclusion of pigment (C) not only improves the yellowish hue of the recycled polyester resin and has a bluing effect, but also promotes the crystallization of the recycled polyester resin, shortening the time required for the crystallization process and improving productivity. Pigment (C) is preferably an organic pigment such as a phthalocyanine pigment or an anthraquinone pigment because of its high transparency and high crystallization promotion effect, and phthalocyanine pigments are particularly preferred because of their good hue.

[0064] In addition, the pigment (C) is preferably a blue pigment, but if only a blue coloring material is added to a yellowish recycled polyester resin, the hue may become greenish, and in particular in the case of beverage bottles, food trays, etc., a greenish hue is undesirable because it is reminiscent of mold. Therefore, the pigment used in the present invention may contain other pigments in addition to the pigment (C), and preferably contains at least one of organic pigments, quinacridone pigments and perylene pigments. By using these pigments, it is possible to obtain a recycled polyester resin with a better 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 obtain good dispersibility of the pigment (C) and good appearance of the molded product.

[0066] The total 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) from the viewpoint of pigment dispersibility and the appearance of the recycled polyester resin. When pigment (C) and other pigments are contained, the blending 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 using the above blending amount, 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. An example of an anthraquinone pigment is Pigment Blue 60. An example of a cobalt 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). A specific example of anthraquinone pigment is LIONOGEN BLUE R (Pigment Blue 60, manufactured by Toyo Color Co., Ltd.). Examples of cobalt pigments include 42-255A (manufactured by TOMATEC, Pigment Blue 28). Examples of ultramarine include Ultramarine No. 1500 (Pigment Blue 29, manufactured by Daiichi Kasei Co., Ltd.) and Premier VU (Pigment Violet 15, manufactured by Tetsutani Co., Ltd.).

[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, Pigment Red 149, and the like.

[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), FASTOGEN SUPER RED 209 228-6736 (manufactured by DIC Corporation, Pigment Red 209), etc. 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), Paliogen Red K 3580 (manufactured by Sun Chemical Co., Ltd., Pigment Red 149), etc.

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

[0073] <Molded body> The molded article is produced 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 variation and molding line contamination, and has excellent transparency and appearance, and therefore can be used in various applications. In particular, even when used in beverage containers and food contact containers such as trays, cups, and films, the recycled polyester resins and molded articles do not leach out the bluing agent into the contents or transfer odors. Furthermore, at the time of filing the application, it is impossible or almost impractical to directly identify the recycled polyester resin and molded article by its structure or characteristics.

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

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, parts and % are by mass, unless otherwise specified. In addition, blanks 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, polyether ester resin, viscosity at 25°C: 30 mPa·s, decomposition temperature: 300°C) A'-4: BIOCIZER (manufactured by 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, surfactant: hydrogenated castor oil) B-3: MS-6 (manufactured by Nitto Kasei Kogyo Co., Ltd., surfactant: magnesium 12-hydroxystearate)

[0078] <Pigments (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, Mitsui Chemicals, IV: 0.84 dL / g) was blown using an injection blow molding machine (Nissei ASB Machinery Co., Ltd.) to obtain a PET bottle. The bottle was then crushed into flakes using a crusher (Nihon 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 and 160° C. for 4 hours. Step [3a]: The dried resin flakes were pelletized at 280°C using a single-screw extruder (manufactured by Thermoplastics) (IV: 0.72 dL / g). Step [4a]: The obtained pellets were crystallized at atmospheric pressure and 140° C. in a dryer (manufactured by Matsui Manufacturing Co., Ltd.). 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, Mitsui Chemicals, IV: 0.84 dL / g) was blown using an injection blow molding machine (Nissei ASB Machinery Co., Ltd.) to obtain a PET bottle. The bottle was then crushed into flakes using a crusher (Nihon 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 and 160°C for 4 hours. Step [3bY]: The dried resin flakes were subjected to liquid phase polymerization at 300°C under vacuum for 30 minutes using an LSP liquid phase polymerization apparatus (manufactured by ACERETECH) and 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 and 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 the liquid dispersion medium (A-1), 0.025 parts by mass of the dispersant (B-1), and 0.25 parts by mass of the 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 liquid colored resin composition were mixed to obtain a mixture. The 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 the liquid dispersion medium (A-1), 0.025 parts by mass of the dispersant (B-1), and 0.25 parts by mass of the 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 the manufacturing method of 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> Except for changing the materials and blending amounts (parts by mass) to those shown in Tables 1 and 2, respectively, liquid colored resin compositions were produced in the same manner as the liquid colored resin composition of Example 2. <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 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 the liquid dispersion medium (A-1), 0.025 parts by mass of the dispersant (B-1), and 0.25 parts by mass of the 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 pelletized to obtain recycled polyester resin 18. That is, the addition of the liquid colored resin composition was simultaneous 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 the liquid dispersion medium (A-1), 0.025 parts by mass of the dispersant (B-1), and 0.25 parts by mass of the pigment (C-1) were mixed and dispersed in a bead mill to obtain a liquid colored resin composition. <Production of recycled polyester resin> A recycled polyester resin was obtained by mixing 0.1 part by mass of the liquid colored resin composition with 100 parts by mass of the recycled polyester resin (a) obtained in the step [5] of Reference Example (a). 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. 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 are described as Reference Example 1. The results of the recycled polyester resin (b) obtained by the production method (b) were similar to those of Reference Example 1.

[0087] <Productivity> In process [4] during the production of each recycled polyester resin, sampling was performed 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 (min) 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 use possible NG: Tc≧120, not practical

[0088] <Dispersibility> Using the obtained recycled polyester resin, 50 plates measuring 150 mm x 130 mm x 2.0 mm were made using an injection molding machine (Toshiba Machine Co., Ltd., injection pressure 100 t). The surfaces of five randomly selected plates were observed, and the number of plates with black spots resulting from the aggregation of coloring materials was counted and evaluated according to the following criteria. [Evaluation Criteria] +++: No black spots on any of the five plates, very good ++: One plate with visible black spots, good +: Two plates with visible black spots, usable NG: Three or more plates have visible black spots, not suitable for practical use

[0089] <Line contamination> After preparing the plate for evaluating dispersibility, the molding machine hopper and the mold were washed with a cloth, and the degree of adhesion of the liquid colored resin composition and the 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 cloth can be confirmed slightly, good NG: Liquid colored resin composition and coloring material are clearly visible on the cloth. Not suitable for practical use.

[0090] <Hue> The obtained recycled polyester resin was used to produce a plate of 87 mm x 50 mm x 1.5 mm using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., injection pressure 60t). 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.> The molded articles were evaluated for elution and odor using the following methods when used in beverage bottles, etc. When used in beverage bottles, etc., if the evaluation of elution or odor is NG, it can be said that the product is not suitable for practical use. <Dissolution> The plate used for the hue evaluation was cut into a size of 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 (manufactured by 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 380-770 nm is 0.02<ε≦0.03, practical use possible NG: absorbance at 380-770 nm is ε>0.03, not practical

[0093] <Odor> 300mL of mineral water and one of the plates used in the hue evaluation were added to a 450mL mayonnaise bottle, and the bottle was left to stand in a 40℃ oven for 1 hour, after which it was vigorously heated. The plate was 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 felt an odor, good +: Two panelists felt odor, practical NG: Three or more panelists detected an odor, not practical

[0094] [Table 1]

[0095] [Table 2]

[0096] As shown in Tables 1 and 2, the manufacturing method of the present invention has produced a recycled polyester resin with excellent hue and productivity, and it has been confirmed that by using this recycled polyester resin, a molded article with excellent transparency and appearance can be obtained without shot-to-shot variation or line contamination. Furthermore, it has been confirmed that the recycled polyester resin and molded article can be obtained without leaching of coloring materials into the contents or odor transfer, and therefore can be suitably used for 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 carrying out polymerization of 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 amount of the liquid colored resin composition added is 0.005 to 1.0 parts by mass per 100 parts by mass of the dry resin flakes, 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 onset temperature of 250° C. or more; The pigment (C) is at least one selected from the group consisting of phthalocyanine pigments, anthraquinone pigments, cobalt pigments, and ultramarine blue; The content of the pigment (C) in the liquid colored resin composition is 0.01 to 20 parts by mass based on 100 parts by mass of the liquid dispersion medium (A), The content of the dispersant (B) in the liquid colored resin composition is 0.5 to 30 parts by mass relative to 100 parts by mass of the pigment (C); A method for producing recycled polyester resin. Step [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 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. 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. A liquid colored resin composition for use in the method for producing the recycled polyester resin according to any one of claims 1 to 4.

6. A recycled polyester resin produced by the method according to any one of claims 1 to 4, The resulting recycled polyester resin is molded into a molded article.

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