Method for identifying recycled polyester resin compositions, identified polyester raw materials, and method for manufacturing polyester resin products

Abstract

To provide a method for identifying polyester resin compositions using chemical tags, identified polyester raw materials, and a method for manufacturing polyester resin products.SOLUTION: There is provided a method for identifying recycled polyester resin that requires the following condition (a). (a) The chemical tag possesses seven or more conjugated double bonds.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for identifying polyester resin compositions using chemical tags, and a method for producing the identified polyester raw materials and polyester resin products. [Background technology]

[0002] Polyesters have excellent mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and are used in a variety of applications. Among polyesters, polyethylene terephthalate (hereinafter referred to as PET) in particular has excellent transparency and processability, so it is widely used in applications that require high quality, such as optical films and release films. However, in the case of process films such as release films, they are disposed of after use, and in recent years there has been a demand for reducing the environmental impact.

[0003] One way to reduce environmental impact is to use thermal recycling, which involves burning discarded polyester resin to obtain thermal energy. However, because thermal recycling generates carbon dioxide and results in a loss of polyester resin, it is necessary to use new petroleum-based raw materials to reproduce polyester.

[0004] There are methods of recycling that do not use new petroleum raw materials, such as material recycling and chemical recycling, but when recycling recovered polyester resin, it is necessary to identify the recovered polyester resin in order to control the quality of the recycled product.

[0005] To address these issues, Patent Document 1 discloses a technology that uses dimethyl terephthalate, which is composed of carbon and / or hydrogen isotopes, as a chemical tag.

[0006] Furthermore, Patent Document 2 discloses a technique that uses porous silica particles as chemical tags. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2002-173523 [Patent Document 2] Patent Publication No. 2023-041656 Summary of the Invention [Problem to be solved by the invention]

[0008] In Patent Document 1, dimethyl terephthalate composed of carbon and / or hydrogen isotopes is used as a chemical tag, which increases the cost of recycled products.

[0009] In Patent Document 2, porous silica particles are used as chemical tags, and therefore, when used in applications where the use of particles is not desirable, such as optical applications, they become foreign matter.

[0010] An object of the present invention is to provide a method for identifying recycled polyester resin compositions using chemical tags that do not affect the quality of the recycled product, and a method for producing polyester raw materials and polyester resin products identified by the method. [Means for solving the problem]

[0011] As a result of intensive research aimed at solving the above problems, the present invention has been achieved, including a method for identifying recycled polyester resin compositions, the identified polyester raw materials, and a method for producing polyester resin products.

[0012] The object of the present invention is achieved by the following means.

[0013] (1) A method for identifying a recycled polyester resin composition, which satisfies the following condition (a): (a) The chemical tag has seven or more conjugated double bonds.

[0014] (2) A method for determining a recycled polyester resin composition according to (1), which satisfies the following condition (b): (b) The detected amount of the chemical tag is equal to or greater than 0.1 ppm (mass) and less than 10,000 ppm (mass).

[0015] (3) The method for identifying a recycled polyester resin composition according to (1), wherein the chemical tag has a structure of (Chemical Formula 1).

[0016] [ka]

[0017] R1 and R2 are each independently a substituent group including hydrogen, an alkyl group, an alkoxy group, an alcohol, a carboxylic acid, an ester, and an ether. n is an integer greater than or equal to 1

[0018] (4) The method for identifying a recycled polyester resin composition according to (1), wherein the chemical tag has a stilbene structure and / or a diphenylbutadiene structure.

[0019] (5) The method for identifying a recycled polyester resin composition according to (1), wherein the chemical tag is detected using liquid chromatography.

[0020] (6) The method for identifying a recycled polyester resin composition according to (1), wherein the chemical tag is detected using fluorescence intensity measurement.

[0021] (7) A method for identifying a recycled polyester resin composition according to (1), wherein the recycled polyester resin composition is obtained by recycling a polyester resin composition derived from used polyester products and / or scraps generated in the polyester product manufacturing process.

[0022] (8) A polyester raw material comprising a recycled polyester resin composition containing a chemical tag having seven or more conjugated double bonds.

[0023] (9) A method for producing a polyester resin product containing a recycled polyester resin composition, comprising at least a first step of detecting the content of chemical tags in the recycled polyester resin composition, a second step of determining the blending amount of the recycled polyester resin composition, and a third step of producing a polyester resin product, wherein the first step satisfies the following condition (c): (c) The chemical tag has seven or more conjugated double bonds.

[0024] (10) The method for producing a polyester resin product according to (9), wherein the second step satisfies the following condition (d):

[0025]

number

[0026] where c j is the content (ppm) of chemical tags in the recycled polyester resin composition and / or virgin polyester resin composition, V j is the blending ratio (wt%) of the recycled polyester resin composition and / or virgin polyester resin composition, and j is a natural number.

[0027] (11) A method for producing a polyester film using the method for producing a polyester resin product according to (9).

[0028] (12) A method for producing polyester fibers using the method for producing a polyester resin product according to (9). [Effects of the Invention]

[0029] According to the present invention, recycled polyester resin compositions can be identified simply and easily without affecting the quality of the recycled product, and high-quality recycled polyester products can be obtained by using the polyester raw materials identified by the above method and the method for producing polyester resin products. DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention will be described in detail below, but the present invention is not limited to the embodiments described below.

[0031] The method for determining whether a recycled polyester resin composition is a recycled polyester resin composition of the present invention must satisfy the following requirement (a). (a) The chemical tag has seven or more conjugated double bonds.

[0032] The conjugated double bond in the present invention refers to a structure in which multiple carbon double bonds and single bonds are alternately connected, and can be represented by (Chemical Formula 2).

[0033] [ka]

[0034] R3 and R4 each independently represent a functional group containing hydrogen, a hydrocarbon group, oxygen, nitrogen, or halogen. m represents an integer of 1 or more.

[0035] The number of conjugated double bonds in the present invention refers to m of the longest conjugated double bond contained in the chemical tag.

[0036] The recycled polyester resin composition of the present invention includes a polyester resin composition recycled from a polyester resin composition derived from used polyester products and / or scrap generated in the polyester product manufacturing process, which will be described later. The recycled polyester resin composition preferably contains 20% by mass or more, more preferably 80% by mass or more, and even more preferably 100% by mass of the polyester resin composition. The recycled polyester resin composition also contains the above-mentioned chemical tag. By including the chemical tag in the recycled polyester resin composition, it becomes possible to identify the recycled polyester resin composition as one that uses a polyester resin composition derived from used polyester products and / or scrap generated in the polyester product manufacturing process.

[0037] When the chemical tag used in the present invention has seven or more conjugated double bonds, the chemical tag can be easily detected by liquid chromatography or fluorescence intensity measurement, which will be described later.

[0038] The detected amount of chemical tags in the recycled polyester resin composition of the present invention is preferably 0.1 ppm (mass) or more but less than 10,000 ppm (mass). More preferably, it is 1 ppm (mass) or more but less than 1,000 ppm (mass). If the detected amount of chemical tags is less than the above lower limit, it may be difficult to accurately detect the content depending on the method for analyzing the chemical tags. Furthermore, if the detected amount of chemical tags exceeds the above upper limit, the physical properties of the recycled polyester resin composition, such as color tone and mechanical properties, may be deteriorated.

[0039] The chemical tag of the present invention preferably has the structure of (Chemical Formula 1).

[0040] [ka]

[0041] R1 and R2 are each independently a substituent group including hydrogen, an alkyl group, an alkoxy group, an alcohol, a carboxylic acid, an ester, and an ether. n is an integer greater than or equal to 1

[0042] The chemical tag (Chemical Formula 1) can be easily analyzed by liquid chromatography, fluorescence intensity measurement, or other methods described below, and is preferable because it does not become a foreign substance in the recycled polyester resin composition and has little effect on the quality of the resin. When conventional inorganic particles or the like are used as chemical tags, foreign substances and a decrease in transparency may occur.

[0043] The chemical tag in the present invention preferably has a stilbene structure and / or a diphenylbutadiene structure, which is preferable because the chemical tag has a stilbene structure and / or a diphenylbutadiene structure, which has little effect on the physical properties, such as the color tone and mechanical properties, of the recycled polyester resin composition.

[0044] The chemical tag of the present invention is preferably detected using liquid chromatography, which is preferable because the chemical tag can be separated from other components contained in the recycled polyester resin composition and analyzed.

[0045] The chemical tags of the present invention are preferably detected using fluorescence intensity measurement, which is preferred because it allows for simple and convenient detection of chemical tags.

[0046] The recycled polyester resin composition of the present invention is preferably a polyester resin composition obtained by recycling a polyester resin composition derived from used polyester products and / or scraps generated in the polyester product manufacturing process. The recycling method may be chemical recycling or material recycling. The chemical recycling described here refers to a polyester resin composition obtained by depolymerizing a polyester resin composition derived from used polyester products and / or scraps generated in the polyester product manufacturing process, and then repolymerizing it after purification treatment or the like. The material recycling refers to a polyester resin composition obtained by pulverizing, washing, removing foreign matter, or the like as necessary from a polyester resin composition derived from used polyester products and / or scraps generated in the polyester product manufacturing process.

[0047] The polyester raw material in the present invention is a recycled polyester resin composition containing a chemical tag having seven or more conjugated double bonds. The polyester raw material is, for example, an aggregate of 1,000 or more chips of recycled polyester resin composition or an aggregate of film scraps and / or fiber scraps and / or bottle scraps, and is an aggregate of recycled polyester resin compositions determined to contain a chemical tag using the recycled polyester resin composition determination method of the present invention. Because the amount of chemical tag contained in the polyester raw material has been determined, it is possible to determine the virgin raw material and the blending amount of the polyester raw material when producing a polyester resin product, as described below. The virgin raw material described here refers to an unused polyester resin composition produced using petroleum-derived or bio-derived raw materials.

[0048] The method for producing a polyester resin product in the present invention includes at least a first step of detecting the content of chemical tags in a recycled polyester resin composition, a second step of determining the blending amount of the recycled polyester resin composition, and a third step of producing a polyester resin product, and the first step must satisfy the following condition (c): (c) The chemical tag has seven or more conjugated double bonds.

[0049] In the method for producing a polyester resin product of the present invention, the second step preferably satisfies the following condition (d).

[0050]

number

[0051] where c j is the content (ppm) of chemical tags in the recycled polyester resin composition and / or virgin polyester resin composition, V jis the blending ratio (wt%) of the recycled polyester resin composition and / or virgin polyester resin composition, and j is a natural number. If the content of the chemical tag is below the lower limit, it may be difficult to accurately detect the content depending on the method of analyzing the chemical tag. Furthermore, if the content of the chemical tag exceeds the upper limit, it may result in a deterioration in physical properties such as color tone and mechanical properties of the polyester resin product.

[0052] Polyester resin products obtainable by the present invention include fibers, films, sheets, containers, bottles, and the like. Among these, the polyester resin products obtained by the production method of the present invention are suitable for polyester films and polyester fibers due to their excellent color tone and transparency, and are particularly suitable for use as biaxially oriented polyester films for process release applications. Films for such applications become unnecessary after release and are suitable for use as recycled raw materials. Recycling them for such applications is also preferred from the perspective of a circular economy. Specific examples of such process release films include release films for multilayer ceramic capacitor (MLCC) manufacturing, films for dry film resists, polarizing plate release films, and optical release films, and the polyester raw material obtainable by the present invention can be used effectively.

[0053] In the polyester film or polyester fiber of the present invention, the polyester raw material obtained by the present invention preferably accounts for 3 mass % or more of the total, more preferably 10 mass % or more, and even more preferably 20 mass % or more, with no particular upper limit.

[0054] In the polyester raw materials used for the polyester film and polyester fiber of the present invention, components other than the recycled polyester resin composition obtained by the present invention are not particularly limited, and conventionally known resin compositions can be used, such as polyester resin compositions obtained from virgin raw materials, polyester resin compositions obtained by other chemical recycling methods, polyester resin compositions obtained by material recycling methods, and copolymer polyester resin compositions. The polyester film of the present invention may be either a single-layer film or a laminate film having two or more layers laminated together, and the stretching form is not particularly limited, and may be an unstretched film, a uniaxially stretched film, a biaxially stretched film, or the like, although a biaxially stretched film is preferred from the viewpoint of mechanical strength.

[0055] The following is an example of a method for producing a film according to the present invention, but the present invention is not limited to this example.

[0056] Various polyester raw materials, including the recycled polyester resin composition, are fed into extruders corresponding to each layer and subjected to hot-melt extrusion. The layers are laminated using a confluence block and co-extruded from a die onto a casting drum cooled to a surface temperature of 10 to 60°C. The resulting film is then cooled and solidified by static electricity, forming an unstretched film. The polyester raw materials molten in the extruder are preferably filtered through a filter. Because even the smallest foreign particles can become large protrusions or defects in the film, it is effective to use a high-precision filter capable of capturing at least 95% of foreign particles 5 μm or larger.

[0057] Next, this unstretched film is introduced into a group of rolls heated to a temperature of 70 to 140°C, stretched 3 to 4 times in the longitudinal direction (longitudinal direction, i.e., the direction in which the sheet travels), and cooled with a group of rolls heated to a temperature of 20 to 50°C. Subsequently, while holding both ends of the sheet with clips, the sheet is introduced into a tenter and stretched 3 to 4 times in the direction perpendicular to the longitudinal direction (width direction) in an atmosphere heated to a temperature of 80 to 240°C. After stretching, the film may be subjected to a relaxation treatment of 0.1 to 5% in the longitudinal and / or width directions. The biaxial stretching method may be either the sequential biaxial stretching method in which stretching in the longitudinal and width directions is performed separately as described above, or a simultaneous biaxial stretching method in which stretching in the longitudinal and width directions is performed simultaneously.

[0058] The following is an example of a method for producing fibers according to the present invention, but the present invention is not limited to this example.

[0059] The resulting polyester resin composition and various other polyester raw materials are fed into an extruder, filtered through a 95 mm diameter, 15-micron nonwoven filter at a spinning temperature of 220°C to 300°C, and discharged from a spinneret nozzle. The discharged yarn is cooled and solidified with cooling air from a cooling chimney, and then focused and lubricated 2 m below the spinneret with an oiling device (1% by mass of pure oil applied relative to the fiber weight). Pre-entanglement is performed using compressed air at an operating pressure of 0.25 MPa through an entanglement nozzle, and the yarn is taken up by a first godet roll and a second godet roll to form a cheese package wound with the undrawn yarn. The resulting undrawn yarn is then draw-twisted using a disc false-twisting machine at a heater temperature of 105 to 210°C, a draw speed of 30 to 1,000 m / min, and a draw ratio of 1.02 to 7.0 to obtain a textured yarn. [Example]

[0060] The present invention will be described in more detail below with reference to examples. The physical properties in the examples were measured by the following methods.

[0061] (1) Chemical tag detection method The detection of chemical tags contained in the recycled polyester resin composition and polyester resin product was carried out by high-performance liquid chromatography (HPLC) measurement of bis-(2-hydroxyethyl) terephthalate (BHET) compositions obtained by depolymerizing the recycled polyester resin composition and polyester resin product.

[0062] (2) Depolymerization of the recycled polyester resin composition was carried out by the following method.

[0063] 100 parts by mass of the recycled polyester resin composition, 200 parts by mass of ethylene glycol, and 0.5 parts by mass of sodium hydroxide were charged into a reaction vessel, and depolymerization was carried out while gradually increasing the temperature. When the internal temperature reached 203°C, depolymerization was terminated, and the vessel was allowed to cool to 25°C. Solid-liquid separation was carried out, and a depolymerized product containing impurities was obtained as the solid content.

[0064] To this depolymerized product, 1000 parts by mass of water was added per 100 parts by mass of the recycled polyester resin composition used, and the mixture was dissolved at 100°C and then filtered using a 1.0 μm filter. The resulting filtrate was cooled to crystallize the BHET composition, and filtered using 5B filter paper to obtain wet crystals of the BHET composition as a solid. The wet crystals of the BHET composition obtained were dried to obtain the BHET composition.

[0065] (3) HPLC was performed as follows. Equipment: Ultimate 3000 (Thermo Fisher Scientific) Column: reversed phase column Mobile phase: A: 10mmol / L ammonium acetate aqueous solution, B: acetonitrile Gradient conditions

[0066] The content of chemical tags was calculated using a calibration curve prepared by HPLC, and whether or not the composition was a recycled polyester resin composition was determined according to the following criteria, with ◯ indicating that the composition was a recycled polyester resin composition and × indicating that the composition was not a recycled polyester resin composition. 〇: Chemical tag content is 0.1 ppm or more ×: Chemical tag content is less than 0.1 ppm.

[0067] (4) How to determine whether polyester products are recyclable The recyclability of polyester products was determined by measuring the fluorescence emission intensity.

[0068] The fluorescence emission intensity was measured by the following method.

[0069] A polyester film was laid out and the emission spectrum was measured under the following conditions. The emission intensity was normalized by the excitation light intensity of each wavelength. The wavelength dependency of the detection sensitivity of the spectrometer was also corrected, and dark count correction was performed. Device: Fluorolog 3-22 (Horiba Jobin Yvon) Light source: Xenon lamp Detector: PMT Excitation wavelength: 350 nm Observation wavelength: up to 750 nm (2 nm intervals) Excitation side slit width: 2 nm Observation side slit width: 2 nm Time constant: 0.2s Measurement mode: Sc / Rc Observation position: 22.5° to the excitation light

[0070] (5) Emission peak intensity The emission peak intensity at each wavelength was determined from the obtained emission spectrum.

[0071] To determine whether a polyester product is recyclable, if the relationship between the 550 nm emission peak intensity and the 370 nm emission peak intensity under 350 nm excitation light satisfies the following formula (1), the product is deemed to be recycled, and this is indicated by a circle. If the following formula (1) is not satisfied, the product is deemed not to be recycled, and this is indicated by an X. The addition of chemical tags increases the 550 nm emission peak intensity, and the ratio (550 nm emission peak intensity) / (370 nm emission peak intensity) increases. Adding chemical tags in an amount exceeding the upper limit of the following formula (1) can cause the physical properties of the polyester product to deteriorate, so polyester products were determined to be recycled if the following formula (1) is satisfied. 5.0≦(550 nm emission peak intensity) / (370 nm emission peak intensity)×100≦20.0 (Equation 1)

[0072] (6) Color tone of polyester film A 100mm x 100mm sample was cut from a polyester film to be measured at a random point. Using a Konica Minolta CM-3600d spectrophotometer, the sample was positioned so that the angle between the normal to the film plane and the incident light was 0°. The chromaticity b* of a random point on the sample was measured using transmitted light under a target mask with a measurement diameter of 25.4mm. The sample was then moved to a position at least 30mm from the center of the measurement point, and the same measurement was repeated four times (measurements were taken at five random points). The chromaticity b* was evaluated according to the following criteria, with ◎ and ○ representing pass. ◎: Less than 1.5 ○: 1.5 or more and less than 3.0 △: 3.0 or above.

[0073] (7) Transparency of polyester film Transparency was evaluated by haze (%). Haze was measured using a turbidity meter "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd. after leaving the polyester film for 1 hour under normal conditions (temperature 23°C, relative humidity 65%). The average value of three measurements was taken as the haze of the polyester film. Haze was evaluated according to the following criteria, with ⊚ and ◯ being considered acceptable. ◎: Less than 1.0 ○: 1.0 or more and less than 2.0 △: 2.0 or above.

[0074] (8) Bending resistance of polyester film In accordance with JIS P8115, samples were cut from the film in the longitudinal and transverse directions, each measuring 110 mm in length (measurement direction) and 15 mm in width, and subjected to a bending test with a load of 1000 g, a bending angle of 135° left and right (R: +135°, L: -135°), a bending speed of 175 times / min, and a chuck tip radius of 0.38 mm. The number of bendings until the film broke was defined as the film's fold resistance. The test was conducted three times in each of the longitudinal and transverse directions, and the average value was used. The fold resistance was evaluated according to the following criteria, with ◎ and 〇 representing passing. Equipment: Mize Testing Machine No. 702. ◎: Break resistance over 10,000 times 〇: Break resistance is 5,000 times or more but less than 10,000 times △: Break resistance less than 5000 times.

[0075] (9) Spinnability of polyester fiber A polyester resin composition containing a recycled polyester resin composition was vacuum dried at 150°C for 10 hours, then fed into an extruder and filtered through a 95mm diameter, 15-micron nonwoven filter at a spinning temperature of 293°C. The molten polyester was extruded at a rate of 70 g / min through a spinneret nozzle with 96 round holes, each 0.25mm in diameter and 0.35mm deep. The extruded yarn was cooled and solidified with cooling air at 0.5 m / s through a cooling chimney. It was then collected and oiled 2 m below the spinneret using an oiling device while being bundled. An oiling agent was applied (1% by mass of pure oil based on the fiber weight). The yarn was pre-entangled using compressed air at an operating pressure of 0.25 MPa through an entanglement nozzle. The yarn was then taken up by first and second godet rolls at a peripheral speed of 2750 m / min to form a cheese package containing 12 kg of 130 dtex, 48 filament undrawn yarn. The winder peripheral speed was 2720 m / min. At this time, the number of times (times / ton) that the yarn broke was counted and evaluated according to the following criteria, with ⊚ and ◯ being considered as passing. ◎: 1.0 times / ton or less 〇: More than 1.0 times / ton and 1.5 times / ton or less △: More than 1.5 times / ton.

[0076] Example 1 100 parts by mass of used polyethylene terephthalate film for process release, 200 parts by mass of ethylene glycol, and 0.5 parts by mass of sodium hydroxide were placed in a reaction vessel, and depolymerization was carried out while gradually increasing the temperature. When the internal temperature reached 203°C, depolymerization was terminated and the vessel was allowed to cool to 25°C. Solid-liquid separation was carried out, and a depolymerized product containing impurities was obtained as the solid content.

[0077] To this depolymerized product, 1000 parts by weight of water was added per 100 parts by weight of used polyethylene terephthalate film for process release. The mixture was dissolved at 100°C, and then 10 parts by weight of activated carbon per 100 parts by weight of used polyethylene terephthalate film for process release was added. The mixture was heated and stirred, and after 60 minutes, the activated carbon was removed using a 1.0 μm filter. The resulting filtrate was cooled to crystallize the BHET composition, and filtered using No. 5B filter paper to obtain wet crystals of the BHET composition as a solid. The resulting wet crystals of the BHET composition were dried to obtain the BHET composition.

[0078] The entire BHET composition obtained by the depolymerization reaction was added to a polymerization reactor and melted at 200°C. 0.01 parts by mass of a polyester resin composition capable of obtaining diantimony trioxide as a polycondensation reaction catalyst was added based on 100 parts by mass of a polyester resin composition capable of obtaining 4,4'-stilbenedicarboxylic acid having seven conjugated double bonds as a chemical tag. -5 After adding 0.1 ppm by mass of the ester, the temperature inside the reactor was gradually increased to 290°C while the pressure inside the reactor was reduced to 1 Torr or less. As the polymerization reaction progressed, the viscosity of the reactant increased, and the reaction was terminated when the stirring torque increase value of the reactant reached the target value for polymerization termination, and the polyester was discharged from the polymerization reactor into the water layer. The discharged polyester was cooled in the water layer and cut into chips with a cutter to obtain a polyester resin composition (Resin A).

[0079] More than 1000 chips of the obtained resin A were packed into a flexible container bag and used as a polyester raw material.

[0080] The properties of the obtained resin A and the form of the polyester raw material are shown in Table 1. The amount of chemical tag detected in resin A was 0.1 ppm or more, and resin A was identified as a recycled polyester resin composition.

[0081] Examples 2 to 4 Polyester resins (resins B to D) and polyester raw materials were obtained in the same manner as in Example 1, except that the amounts of chemical tags added were changed as shown in Table 1.

[0082] The properties of the obtained Resins B to D and the form of the polyester raw material are shown in Table 1. The detected amount of chemical tags in all of Resins B to D was 0.1 ppm or more, and Resins B to D were identified as recycled polyester resin compositions.

[0083] Example 5 A used polyethylene terephthalate film for process release laminated with a silicone release layer was washed by immersion in a 1 mol / L aqueous NaOH solution at 80°C for 15 minutes, then rinsed with water and dried by blowing hot air. The dried film was crushed, and 0.1 parts by mass (1000 ppm) of 4,4'-stilbenedicarboxylic acid was added as a chemical tag to 100 parts by mass of the used polyethylene terephthalate film for process release, and the mixture was mixed to obtain a flake-shaped polyester resin composition (Resin E).

[0084] The obtained flakes of Resin E were packed together in a flexible container bag and used as a polyester raw material.

[0085] The properties of the obtained Resin E and the form of the polyester raw material are shown in Table 1. The amount of chemical tag detected in Resin E was 0.1 ppm or more, and Resin E was identified as a recycled polyester resin composition.

[0086] Example 6 A polyester resin (resin F) and a polyester raw material were obtained in the same manner as in Example 1, except that the depolymerized BHET was not purified using activated carbon.

[0087] The properties of the obtained Resin F and the form of the polyester raw material are shown in Table 1. The amount of chemical tag detected in Resin F was 0.1 ppm or more, and Resin F was identified as a recycled polyester resin composition.

[0088] Example 7 A polyester resin composition (resin G) and a polyester raw material were obtained in the same manner as in Example 5, except that no chemical tag was added.

[0089] The properties of the obtained Resin G and the form of the polyester raw material are shown in Table 1. The amount of chemical tag detected in Resin G was 0.1 ppm or more, and Resin G was identified as a recycled polyester resin composition.

[0090] (Comparative Example 1) A polyester resin composition (resin H) and a polyester raw material were obtained in the same manner as in Example 1, except that no chemical tag was added.

[0091] The properties of the obtained Resin H and the form of the polyester raw material are shown in Table 1. The amount of chemical tags in Resin H was measured, but none were detected, so it was determined that Resin H was not a recycled polyester resin composition.

[0092] (Comparative Examples 2 to 3) Polyester resins (Resins I to J) and polyester raw materials were obtained in the same manner as in Example 1, except that the compounds and amounts of the chemical tags added were changed as shown in Table 1. Note that 4,4'-dihydroxybiphenyl has six conjugated double bonds, and silica particles have zero conjugated double bonds.

[0093] The properties of the obtained Resins I to J and the form of the polyester raw material are shown in Table 1. The amounts of chemical tags in Resins I to J were measured, but none were detected, so it was determined that Resins I to J were not recycled polyester resin compositions.

[0094] Comparative Example 4 A slurry consisting of 86 parts by mass of petroleum-derived terephthalic acid and 37 parts by mass of petroleum-derived ethylene glycol (1.15 times the molar ratio of terephthalic acid) was gradually added to an esterification reactor charged with 105 parts by mass of petroleum-derived bishydroxyethyl terephthalate dissolved at 255°C, and the esterification reaction was allowed to proceed. The temperature within the reaction system was controlled to 245-255°C, and the esterification reaction was terminated when the reaction rate reached 95%.

[0095] 105 parts by mass of the 255°C esterification product (corresponding to 100 parts by mass of polyester resin composition) was transferred to a polymerization reactor, and 0.01 parts by mass of antimony trioxide was added as a polymerization catalyst (based on 100 parts by mass of the polyester resin composition). The temperature inside the reactor was gradually raised to 290°C, while the pressure inside the reactor was reduced to 1 Torr or less. As the polymerization reaction progressed, the viscosity of the reactants increased. The reaction was terminated when the increase in the stirring torque of the reactants reached the target value for polymerization termination, and the polyester was discharged from the polymerization reactor into the aqueous layer. The discharged polyester was cooled in the aqueous layer and cut into chips with a cutter to obtain a polyester resin composition (Resin K).

[0096] More than 1000 chips of the obtained resin K were packed in a flexible container bag and used as a polyester raw material.

[0097] The properties of the obtained Resin K and the form of the polyester raw material are shown in Table 1. The amount of chemical tags in Resin K was measured, but none were detected, so it was determined that Resin K was not a recycled polyester resin composition.

[0098] [Table 1]

[0099] Example 8 A polyester film was obtained using Resin A by the method described below, and was evaluated.

[0100] Resin A was dried under reduced pressure at 160°C for 2 hours and then loaded into an extruder. It was melted at 280°C in the extruder, extruded from the die onto a casting drum with a surface temperature of 25°C, and then cooled and solidified by static electricity to produce an unstretched sheet. The sheet was then preheated with a group of heated rolls and stretched 3.3 times in the longitudinal direction (longitudinal direction, i.e., the sheet travel direction) at 90°C, followed by cooling with a group of rolls at 25°C to obtain a uniaxially stretched film. While holding both ends of the resulting uniaxially stretched film with clips, it was stretched 3.5 times in the direction perpendicular to the longitudinal direction (width direction) in a 110°C heating zone in a tenter. Subsequently, it was heat-set for 10 seconds at 230°C in a heat treatment zone in the tenter. After uniformly and slowly cooling in the cooling zone, both ends of the film that were held by the tenter clips were cut off and wound up to obtain a polyester film with a thickness of 25 μm.

[0101] The properties of the obtained polyester film are shown in Table 2. The polyester resin composition used in the obtained polyester film was determined to be a recycled product by detecting the amount of chemical tag and measuring the fluorescence emission intensity, and the color tone, transparency, and bending resistance were good.

[0102] Furthermore, polyester fibers were obtained using Resin A by the method described below and were evaluated.

[0103] Resin A was dried under reduced pressure at 150°C for 10 hours and then fed into an extruder. At a spinning temperature of 293°C, the polyester melt was filtered through a 95-mm diameter, 15-micron nonwoven filter and extruded at a rate of 70 g / min through a die nozzle with 95 round holes, each 0.25 mm in diameter and 0.35 mm deep. The extruded yarn was cooled and solidified through a cooling chimney with 0.5 m / s of cooling air. The oil was applied to the extruded yarn while being focused using an oiling device 2 m below the die (1 part by mass of pure oil applied relative to the fiber weight). The yarn was pre-entangled using compressed air at a working pressure of 0.25 MPa through an entanglement nozzle. The yarn was then taken up by the first and second godet rolls at a peripheral speed of 2750 m / min, forming a cheese package containing 12 kg of 130 dtex, 48 filament undrawn yarn. The winder peripheral speed was 2720 m / min.

[0104] The yarn breakage rate was 0.7 times per ton, and the spinnability was good.

[0105] (Examples 9 to 10, 13) Polyester films and polyester fibers were obtained in the same manner as in Example 8, except that the type of resin used was changed as shown in Table 2.

[0106] The polyester films obtained in Examples 9, 10, and 13 were identified as recycled products by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and had good color tone, transparency, and bending resistance. The polyester fibers obtained in Examples 9, 10, and 13 had good spinnability.

[0107] (Examples 11 to 12) Polyester films and polyester fibers were obtained in the same manner as in Example 8, except that the type of resin used was changed as shown in Table 2.

[0108] The polyester films obtained in Examples 11 and 12 were determined to be recycled products by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and although they had a slightly high color tone b value and slightly low bending resistance, they had good transparency. The polyester fibers obtained in Examples 11 and 12 had slightly low spinnability.

[0109] (Examples 14 to 16) A polyester film and polyester fiber were obtained in the same manner as in Example 8, except that the types and blending ratios of the resins used were changed as shown in Table 2.

[0110] The polyester films obtained in Examples 14 to 16 were determined to be recycled products by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and had good color tone, transparency, and bending resistance. The polyester fibers obtained in Examples 14 to 16 had good spinnability.

[0111] (Comparative Example 5) Polyester films and polyester fibers were obtained in the same manner as in Example 8, except that the type of resin used was changed as shown in Table 2.

[0112] The polyester film obtained in Comparative Example 5 was determined to be a non-recycled product by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and had good color tone, transparency, and bending resistance. The polyester fiber obtained in Comparative Example 5 had good spinnability.

[0113] (Comparative Example 6) Polyester films and polyester fibers were obtained in the same manner as in Example 8, except that the resins used were changed as shown in Table 2.

[0114] The polyester film obtained in Comparative Example 6 was determined to be not a recycled product by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and had low transparency, but was good in color tone and bending resistance. The polyester fiber obtained in Comparative Example 6 had good spinnability.

[0115] (Comparative Example 7) Polyester films and polyester fibers were obtained in the same manner as in Example 8, except that the resins used were changed as shown in Table 2.

[0116] The polyester film obtained in Comparative Example 7 was determined to be a non-recycled product by detecting the amount of chemical tags and measuring the fluorescence emission intensity, and had good color tone, transparency, and bending resistance. The polyester fiber obtained in Comparative Example 7 had good spinnability.

[0117] [Table 2] [Industrial Applicability]

[0118] The method for identifying recycled polyester resin compositions, polyester raw materials, and polyester resin products of the present invention are useful for optical applications, agricultural materials, horticultural materials, fishing materials, civil engineering and construction materials, stationery, medical supplies, automotive parts, electrical and electronic parts, clothing fibers, and other applications.

Claims

1. A method for identifying recycled polyester resins, which satisfies the following condition (a): (a) The chemical tag has seven or more conjugated double bonds.

2. The method for determining the recycled polyester resin composition according to claim 1, wherein the following condition (b) is satisfied: (b) The detected amount of chemical tag is 0.1 ppm or more and less than 10,000 ppm.

3. The method for identifying a recycled polyester resin composition according to claim 1, wherein the chemical tag is (Chemical Formula 1). 【Chemistry 1】 R １ , R ２ each independently represents a substituent including hydrogen, an alkyl group, an alkoxy group, an alcohol, a carboxylic acid, an ester, or an ether. n represents an integer of 1 or more.

4. The method for identifying a recycled polyester resin composition according to claim 1, wherein the chemical tag has a stilbene structure and / or a diphenylbutadiene structure.

5. The method for identifying a recycled polyester resin composition according to claim 1, wherein the chemical tag is detected using liquid chromatography.

6. The method for identifying a recycled polyester resin composition according to claim 1, wherein the chemical tag is detected using fluorescence intensity measurement.

7. 2. The method for identifying a recycled polyester resin composition according to claim 1, wherein the recycled polyester resin composition is obtained by recycling a polyester resin composition derived from used polyester products and / or scraps generated in the polyester product manufacturing process.

8. A polyester raw material comprising a recycled polyester resin composition containing a chemical tag having seven or more conjugated double bonds.

9. A method for producing a polyester resin product containing a recycled polyester resin composition, comprising at least a first step of detecting the content of a chemical tag in the recycled polyester resin composition, a second step of determining the blending amount of the recycled polyester resin composition, and a third step of producing a polyester resin product, wherein the first step satisfies the following condition (c): (c) the chemical tag has seven or more conjugated double bonds;

10. The method for producing a polyester resin product according to claim 9, wherein the second step satisfies the following condition (d): [Equation 1] Here, c ｊ is the content (ppm) of chemical tags in the recycled polyester resin composition and / or virgin polyester resin composition, V ｊ is the blending ratio (wt %) of the recycled polyester resin composition and / or virgin polyester resin composition, and j is a natural number.

11. A method for producing a polyester film using the method for producing a polyester resin product according to claim 9.

12. A method for producing polyester fibers using the method for producing a polyester resin product according to claim 9.

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