Method for producing bis-(2-hydroxyethyl)terephthalate composition

Abstract

To provide a method for producing a scarcely colored BHET composition by purifying a depolymerized material obtained by chemically decomposing a polyester resin composition using a suitable adsorbent.SOLUTION: A method for producing a bis-(2-hydroxyethyl)terephthalate composition includes steps (a) to (d) and satisfies conditions (i) to (iii). (a) A step of depolymerizing a polyester resin composition. (b) A step of adding a solvent to a depolymerized material, dissolving the solvent, and obtaining solution A. (c) A step of bringing the solution A into contact with an adsorbent, and obtaining solution B. (d) A step of obtaining a bis-(2-hydroxyethyl)terephthalate composition from the solution B. (i) The addition amount of the solvent in the step (b) is 20 pts.mass or more and 7,000 pts.mass or less of the solvent with respect to 100 pts.mass of the polyester resin composition. (ii) With respect to 100 pts.mass of the solvent in the step (b), 90 pts.mass of water is contained. (iii) The average pore diameter of the adsorbent is 0.5 nm or more and 200 nm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a bis-(2-hydroxyethyl) terephthalate (hereinafter referred to as BHET) composition in chemical recycling.

Background Art

[0002] Polyester is excellent in mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and is used in various applications. Among polyesters, polyethylene terephthalate (hereinafter referred to as PET) is particularly widely used in applications that require high quality, such as optical films and release films, because of its excellent transparency and processability. However, since process films such as release films are discarded after use, there has been a demand for reducing the environmental impact in recent years.

[0003] As a measure to reduce the environmental impact, there is thermal recycling in which waste polyester resin is burned to obtain thermal energy. However, when thermal recycling is performed, carbon dioxide is generated and the polyester raw material is lost. Therefore, it is necessary to newly use petroleum raw materials to reproduce polyester.

[0004] For recycling without newly using petroleum raw materials, there is a method called chemical recycling in which polyester is chemically decomposed into raw materials or intermediates and then repolymerized to reproduce polyester. However, when chemical recycling does not include a step of removing impurities such as dyes and additives during the depolymerization and repolymerization of polyester, the color tone and physical properties of the obtained chemically recycled polyester deteriorate.

[0005] In response to these problems, Patent Document 1 discloses a technique related to a method for recovering ester monomers from fibrous polyester.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Patent Document 1 discloses a method for purifying a glycol solution containing an ester monomer, which is obtained by extracting a coloring component from fibrous polyester using ethylene glycol and further depolymerizing the fibrous polyester using glycol. However, by performing the purification of the ester monomer in the glycol solution, impurities derived from the glycol solution are generated, and problems such as a decrease in the purity of the ester monomer and deterioration of the physical properties of the polyester made from the ester monomer arise.

[0008] An object of the present invention is to provide a method for producing a BHET composition with less coloring, which can obtain a polyester resin composition with good color tone, by purifying a depolymerized product obtained by chemically decomposing a polyester resin composition using a suitable adsorbent.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, a method for producing the BHET composition of the present invention has been achieved.

[0010] The object of the present invention is achieved by the following means.

[0011] (1) A method for producing a bis-(2-hydroxyethyl) terephthalate composition having steps (a) to (d) and satisfying conditions (i) to (iii) for the steps. (a) A step of depolymerizing a polyester resin composition. (b) A step of adding a solvent to the depolymerized product and dissolving it to obtain solution A. (c) A step of bringing solution A into contact with an adsorbent to obtain solution B. (d) A step of obtaining a bis-(2-hydroxyethyl) terephthalate composition from solution B. (i)(b) In the process, the amount of the solvent added is 20 parts by mass or more and 7,000 parts by mass or less with respect to 100 parts by mass of the polyester resin composition. (ii)(b) The solvent in the process contains 90 parts by mass or more of water with respect to 100 parts by mass of the solvent. (iii) The average pore diameter of the adsorbent is 0.5 nm or more and 200 nm or less.

[0012] (2) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the amount of ethylene glycol is 10 parts by mass or less with respect to 100 parts by mass of the solvent in the (b) process.

[0013] (3) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the adsorbent is at least one of activated carbon, zeolite, and silica gel.

[0014] (4) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the pH of the adsorbent is 2 or more and 9 or less.

[0015] (5) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the elemental composition of oxygen when the adsorbent is measured by XPS is 1 atomic% or more and 70 atomic% or less.

[0016] (6) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the content of the compound having 7 or more conjugated double bonds in the obtained bis-(2-hydroxyethyl) terephthalate composition is 0.01 mass ppm or more and 10 mass ppm or less.

[0017] (7) The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to (1), wherein the absorbance at 330 nm when the UV-Vis measurement of the bis-(2-hydroxyethyl) terephthalate composition is performed is 0.3 or less.

[0018] A polyester resin composition obtained by polycondensing the bis-(2-hydroxyethyl) terephthalate composition described in (8)(1).

[0019] (9) The polyester resin composition described in (8), wherein the diethylene glycol content is 2 parts by mass or less.

[0020] (10) A polyester film containing the polyester resin composition described in (9).

[0021] (11) Fibers containing the polyester resin composition described in (9). [Advantages of the Invention]

[0022] The present invention provides a method for producing a BHET composition with less coloring, which can obtain a polyester resin composition with good color tone, by purifying the depolymerized product obtained by chemically decomposing the polyester resin composition using a suitable adsorbent. [Embodiments for Carrying Out the Invention]

[0023] The present invention will be described in detail below.

[0024] In the method for producing the BHET composition of the present invention, in order to obtain the BHET composition, it has the following steps (a) to (d), and it is necessary to satisfy the conditions (i) to (iii) for these steps. (a) A step of depolymerizing the polyester resin composition. (b) A step of adding a solvent to the depolymerized product to dissolve it and obtaining solution A. (c) A step of bringing solution A into contact with an adsorbent to obtain solution B. (d) A step of obtaining a bis-(2-hydroxyethyl) terephthalate composition from solution B. (i) The amount of the solvent added in step (b) is 20 parts by mass or more and 7000 parts by mass or less of the solvent with respect to 100 parts by mass of the polyester resin composition. (ii) With respect to 100 parts by mass of the solvent in step (b), it contains 90 parts by mass or more of water. (iii) The average pore diameter of the adsorbent is 0.5 nm or more and 200 nm or less.

[0025] For the polyester resin composition used in the present invention, it is preferable to use used polyesters such as PET bottles, polyester films, clothes, containers, and scraps generated in the molding process. In particular, a polyester resin composition mainly composed of PET is preferable to obtain a BHET composition, but components other than PET such as copolymer components may be included as long as the effects of the present invention are not impaired. For example, used polyesters such as PET bottles may contain groups derived from isophthalic acid, but a BHET composition can be obtained without problems.

[0026] The depolymerization reaction in the present invention refers to a reaction in which a glycolysis reaction is carried out by heating and stirring a polyester resin composition in the presence of a glycol compound, and finally decomposing it until a BHET composition is obtained.

[0027] In the depolymerization reaction of the present invention, conventionally known depolymerization reaction catalysts and low polymers of the polyester resin composition can be added as long as the effects of the present invention are not hindered.

[0028] In the present invention, when using a depolymerization reaction catalyst, metal hydroxides such as sodium hydroxide, potassium hydroxide, and magnesium hydroxide, and metal acetate salts such as magnesium acetate, manganese acetate, cobalt acetate, calcium acetate, and lithium acetate can be used, but it is not particularly limited thereto.

[0029] In addition, the low polymer of the polyester resin composition refers to those obtained by subjecting dicarboxylic acid compounds such as terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl isophthalate, and glycol compounds such as ethylene glycol to an esterification reaction or a transesterification reaction, or those obtained when the polyester resin composition is subjected to a depolymerization reaction, but is not particularly limited thereto. However, since the low polymer obtained by an esterification reaction or a transesterification reaction is newly produced using raw materials, it is preferable to use the low polymer obtained when the polyester resin composition is subjected to a depolymerization reaction from the viewpoint of environmental load.

[0030] After the depolymerization reaction is carried out in step (a) of the present invention, the method for obtaining the depolymerized product is not particularly limited. For example, a method of evaporating and concentrating the glycol compound contained in the depolymerization reaction solution, a method of lowering the temperature of the depolymerization reaction solution, crystallizing, and taking it out, a method of adding a solvent different from the glycol compound contained in the depolymerization reaction solution and reprecipitating, etc. can be mentioned.

[0031] The solvent added in step (b) of the present invention needs to be 20 parts by mass or more and 7000 parts by mass or less with respect to 100 parts by mass of the polyester resin composition. Further, the lower limit is preferably 350 parts by mass or more, and the upper limit is preferably 5500 parts by mass. When the addition amount of the solvent is less than the above lower limit, the amount of the solvent with respect to the depolymerized product is small, and sufficient stirring in the dissolution container cannot be performed. Therefore, local heating occurs when heating and dissolving, the depolymerized product is thermally decomposed, and the quality of the BHET composition is deteriorated. In addition, when the addition amount of the solvent exceeds the above upper limit, the amount of solvent used and the energy required for treating the solvent after use become extremely large, and the environmental load increases.

[0032] In step (b) of the present invention, it is necessary to contain 90 parts by mass or more of water with respect to 100 parts by mass of the solvent. By satisfying the amount of water in the solvent within the above range, the generation of impurities derived from the glycol compound can be suppressed, and a high-quality BHET composition can be obtained. Further, by satisfying the amount of water in the solvent within the above range, the yield of the obtained BHET composition becomes high. Further, the temperature for dissolving the depolymerized product in the solvent is not particularly limited, but it is preferably 80°C or higher in order to dissolve the depolymerized product.

[0033] In step (c) of the present invention, the temperature of solution A is preferably 80°C or higher, more preferably 90°C or higher. By the temperature of solution A being within the above range or higher, it can be brought into contact with the adsorbent in a homogeneous solution state, the purification efficiency becomes high, and a high-quality BHET composition can be obtained.

[0034] The average pore diameter of the adsorbent used in step (c) of the present invention needs to be 0.5 nm or more and 200 nm or less. More preferably, it is 1.5 nm or more and 50 nm or less. By the average pore diameter of the adsorbent being within the above range, impurities that mainly affect coloring can be removed, and a high-quality BHET composition can be obtained.

[0035] The adsorbent used in step (c) of the present invention is preferably at least one of activated carbon, zeolite, and silica gel. By using at least one of activated carbon, zeolite, and silica gel as the adsorbent, the used adsorbent can be regenerated and reused, so the environmental load can be reduced.

[0036] The pH of the adsorbent used in step (c) of the present invention is preferably 2 or more and 9 or less. By the pH of the adsorbent being within the above range, impurities that mainly affect coloring can be removed, and the generation of diethylene glycol in the polyester resin composition obtained by polycondensing the purified BHET composition can be suppressed.

[0037] When the adsorbent used in step (c) of the present invention is measured by XPS, the elemental composition of oxygen is preferably 1 atomic% or more and 70 atomic% or less. More preferably, it is 1 atomic% or more and 15 atomic% or less. When the elemental composition of oxygen when the adsorbent is measured by XPS is within the above range, impurities that mainly affect coloring can be removed, and the generation of diethylene glycol in the polyester resin composition obtained by polycondensing the purified BHET composition can be suppressed.

[0038] The amount of the adsorbent used in step (c) of the present invention is preferably 1 part by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the polyester resin composition. More preferably, it is 5 parts by mass or more and 100 parts by mass or less. When the amount of the adsorbent used is less than the above lower limit, impurities that mainly affect coloring cannot be sufficiently removed, which may cause a decrease in the quality of the BHET composition. Further, when the amount of the adsorbent used exceeds the above upper limit, the yield of the obtained BHET composition may decrease.

[0039] In step (d) of the present invention, the method for obtaining the BHET composition from solution B is not particularly limited. For example, a method of evaporating the solvent contained in solution B, a method of adding a solvent different from the solvent contained in solution B and reprecipitating, a method of gradually lowering the temperature of solution B to recrystallize the BHET composition (hereinafter referred to as crystallization), etc. can be mentioned. Crystallization is preferred because the purity of the BHET composition can be further increased. It is also preferable to filter solution B with a filter or the like, or to perform centrifugation to remove impurities.

[0040] The glycol compound used in the present invention is preferably ethylene glycol in order to efficiently obtain the BHET composition, but other glycol compounds may be contained as long as the effects of the invention are not impaired.

[0041] It is preferable that the content of the compound having 7 or more conjugated double bonds in the BHET composition obtained by the production method of the present invention is 0.01 mass ppm or more and 10 mass ppm or less. More preferably, it is 0.01 mass ppm or more and 5 mass ppm or less, and still more preferably, it is 0.01 mass ppm or more and 1 mass ppm or less. When the content of the compound having 7 or more conjugated double bonds in the BHET composition is within the above range, the color tone of the polyester resin composition obtained from the BHET composition becomes good.

[0042] The conjugated double bond in the present invention refers to a structure in which a plurality of double bonds and single bonds of carbon are alternately connected, and the conjugated double bond can be represented by (Chemical Formula 1).

[0043]

Chemical Formula

[0044] R1 and R2 each independently represent hydrogen, a hydrocarbon group, or a functional group containing oxygen, nitrogen, or halogen. n represents an integer of 1 or more.

[0045] The number of conjugated double bonds in the present invention is the n of the longest conjugated double bond contained in the chemical tag.

[0046] It is preferable that the BHET composition obtained by the production method of the present invention has an absorbance at 330 nm of 0.3 or less, more preferably 0.1 or less, when UV-Vis measurement is performed. When the absorbance at 330 nm is within the above range, the color tone of the polyester resin composition obtained from the BHET composition becomes good. Note that the UV-Vis measurement refers to measuring the absorbance from UV (ultraviolet region) to Vis (visible light region) after dissolving BHET in a measurement solvent, as also described in the examples.

[0047] The BHET composition obtained by the production method of the present invention can be made into a polyester resin composition by polycondensation.

[0048] The polycondensation reaction in the present invention refers to a process of heating and stirring the BHET composition under reduced pressure to desorb ethylene glycol from the BHET composition and finally obtaining a polyester resin composition. As the reaction catalyst in polycondensation, a conventionally known catalyst can be used, and an antioxidant, a color inhibitor, a phosphorus compound, a pigment, a dye, particles, etc. can also be added as necessary. Further, within a range that does not impair the effects of the present invention, a plurality of other dicarboxylic acid components, diol components, and even hydroxycarboxylic acids may be used for copolymerization.

[0049] The content of diethylene glycol with respect to 100 parts by mass of the polyester resin composition obtained in the present invention is preferably 2 parts by mass or less. When the content of diethylene glycol is within the above range, the heat resistance of the polyester resin composition becomes good.

[0050] By molding the polyester resin composition obtained in the present invention, it can be suitably used for fibers, films, sheets, containers, bottles, etc. Among them, the polyester resin composition obtained using the BHET composition obtained by the production method of the present invention is suitable for polyester films and polyester fibers because of its excellent color tone and transparency, and can be particularly preferably used for biaxially stretched polyester films for mold release in the process. The film for this application becomes unnecessary after mold release and is preferably utilized as a raw material for recycling. Further, recycling for this application is preferable from the viewpoint of circular economy. Specific examples of such a release film for the process include a release film for manufacturing multilayer ceramic capacitors (MLCC), a film for dry film resist, a release film for polarizing plates, and an optical release film, and the polyester resin composition obtained in the present invention can be preferably used.

[0051] In the polyester film and polyester fiber of the present invention, the polyester resin composition obtained in the present invention is preferably 3% by mass or more of the total weight, more preferably 10% by mass or more, and still more preferably 20% by mass or more. Also, the upper limit is not particularly limited.

[0052] In the resin composition used for the polyester film and polyester fiber of the present invention, components other than the polyester resin composition obtained in the present invention are not particularly limited, and polyester resin compositions obtained from virgin raw materials, polyester resin compositions obtained by other chemical recycling, polyester resin compositions obtained by material recycling, and conventionally known resin compositions such as copolymerized polyester resin compositions can be used. Further, the polyester film of the present invention may be either a single-layer film or a laminated film having two or more layers laminated, and the stretching form is not particularly limited, such as an unstretched film, a uniaxially stretched film, or a biaxially stretched film. However, from the viewpoint of mechanical strength, a biaxially stretched film is preferable.

[0053] The method for casting the film in the polyester film of the present invention is not particularly limited. However, a method of heating and melting the polyester resin composition in an extruder and extruding it onto a cooled casting drum from a die to process it into a sheet form (melt casting method), a method of dissolving the polyester resin composition in a solvent, extruding the solution onto a support such as a casting drum or an endless belt to form a film, and then drying and removing the solvent from such a film layer to process it into a sheet form (solution casting method), etc. can also be used. In the case of a laminated film, a method of charging the polyester resin compositions of each layer to be laminated into separate extruders, melting them, then merging them, and co-extruding them onto a cooled casting drum from a die to process them into a sheet form (a method of melt film formation by co-extrusion method) can be preferably used.

[0054] The method for producing the polyester fiber of the present invention is not particularly limited. However, methods such as a method of drying, melting, and extruding (hereinafter referred to as spinning) the polyester resin composition to once wind up the polyester unstretched yarn and then stretching it, a method of continuously performing spinning and stretching, and a method of winding up at high speed after spinning and stretching it by the speed difference can be used.

[0055] The specific production method of the present invention is exemplified below, but it is not limited thereto.

[0056] (a) Add 30 to 600 parts by mass of ethylene glycol to 100 parts by mass of the recovered polyester resin composition such as PET bottle and PET film scraps, and carry out depolymerization in the temperature range of 190°C to 240°C. Gradually lower the temperature of the obtained depolymerization solution, and separate the crystallized depolymerized product and the ethylene glycol contained in the depolymerization solution by filtration or the like to obtain the depolymerized product as a solid content.

[0057] (b) Add 20 to 7000 parts by mass of water to the depolymerized product based on 100 parts by mass of the recovered polyester resin composition used in (a), and dissolve the depolymerized product in water in the temperature range of 80°C to 100°C to obtain Solution A.

[0058] (c) Contact Solution A with at least one adsorbent among activated carbon, zeolite, and silica gel in the temperature range of 80°C to 100°C for 10 to 60 minutes to obtain Solution B.

[0059] (d) Remove foreign substances and the like contained in Solution B by filtration or the like, gradually cool Solution B to crystallize the BHET composition, and obtain crystals of the wet BHET composition as a solid content by filtration or the like. Dry the obtained crystals of the wet BHET composition to obtain the BHET composition.

[0060] Add the obtained BHET composition to a polymerization reaction tank, melt it in the temperature range of about 200°C to 250°C, add a polymerization reaction catalyst such as antimony trioxide, and then gradually increase the temperature inside the apparatus to about 270°C to 300°C while reducing the pressure inside the apparatus to 1 Torr or less. As the polymerization reaction proceeds, the viscosity of the reaction product increases, and when the increase value of the stirring torque of the reaction product reaches the polymerization end target value, the reaction is terminated, and the polyester is discharged from the polymerization reaction tank to a water tank. The discharged polyester is rapidly cooled in the water tank and chipped with a cutter to obtain a polyester resin composition.

[0061] The manufacturing method of the film in the present invention is exemplified below, but it is not limited thereto.

[0062] The various polyester resin compositions containing the obtained polyester resin composition are respectively fed into the extruders corresponding to each layer, heated, melted, and extruded. They are laminated using a merging block and co-extruded onto a cast drum cooled to a surface temperature of 10 to 60°C from a die, and adhered, cooled, and solidified by static electricity to produce an unstretched film. At this time, the polyester resin melted by the extruder is preferably filtered by a filter. Since even very small foreign matters will become large protrusions or defects in the film, it is effective to use a high-precision filter that can collect 95% or more of foreign matters of 5 μm or more.

[0063] Next, this unstretched film is guided to a roll group heated to a temperature of 70 to 140°C, stretched 3 to 4 times in the longitudinal direction (the vertical direction, that is, the advancing direction of the sheet), and cooled by a roll group at a temperature of 20 to 50°C. Subsequently, while gripping both ends of the sheet with clips, it is guided to a tenter and stretched 3 to 4 times in the direction perpendicular to the longitudinal direction (the width direction) in an atmosphere heated to a temperature of 80 to 240°C. Also, after stretching, a relaxation treatment of 0.1 to 5% may be performed in the longitudinal and / or width directions. Note that as the method of biaxial stretching, either the sequential biaxial stretching method in which the stretching in the longitudinal direction and the width direction is performed separately as described above or the simultaneous biaxial stretching method in which the stretching in the longitudinal direction and the width direction is performed simultaneously may be used.

[0064] The method for manufacturing fibers in the present invention is exemplified below, but it is not limited thereto.

[0065] While supplying various polyester resin compositions containing the obtained polyester resin composition to an extruder, filter them through a 15-micron non-woven fabric filter with a diameter of 95 mm at a spinning temperature of 220°C to 300°C, and discharge them from a die nozzle. Cool and solidify the discharged yarn with cooling air by a cooling chimney, apply an oil agent while converging with an oiling device at a position 2 m below the die (apply 1% by mass as pure oil content based on the fiber weight), perform preliminary texturing using compressed air at an operating pressure of 0.25 MPa with an interlacing nozzle, take up with a first godet roll and a second godet roll, and make it into a cheese package wound with an undrawn yarn. Use a disk false twister for the obtained undrawn yarn to perform a drawing false twisting process at a heater temperature of 105 to 210°C, a drawing speed of 30 to 1000 m / min, and a draw ratio of 1.02 to 7.0 times to obtain a processed yarn.

Example

[0066] The present invention will be described in more detail with the following examples. The physical property values in the examples were measured by the following methods.

[0067] (1) Average pore diameter of adsorbent For the adsorbent, nitrogen adsorption measurement was performed at 77 K (liquid nitrogen temperature) to obtain a nitrogen adsorption / desorption isotherm. The pore characteristics of the adsorbent were calculated from the obtained nitrogen adsorption / desorption isotherm. The nitrogen adsorption / desorption isotherm was measured using BELSORP18PLUS-HT manufactured by Nippon Bell Co., Ltd., and the specific surface area was determined by the BET method. Also, the measurement results were analyzed by the GCMC method to calculate the average pore diameter.

[0068] (2) pH of adsorbent Weigh 10 g of the adsorbent and put it into a flask, add 100 mL of ion-exchanged water to the flask, heat it to boiling, hold it for 15 minutes, then filter it, cool the filtrate to room temperature, and measure the pH using a pH meter.

[0069] (3) Elemental composition of oxygen in adsorbent The elemental composition of oxygen was evaluated by performing XPS measurement on the adsorbent. XPS was carried out by the following method. Device: Quantera SXM (manufactured by PHI) Excitation X-ray: monochromatic Al K α1,2 ray X-ray diameter: 200 μm Photoelectron emission angle: 45°

[0070] (4) Yield of the BHET composition The BHET composition obtained by performing depolymerization reaction, crystallization, etc. was vacuum dried at 70 °C under high vacuum for 8 hours or more, and the weight of the powdery BHET composition was measured. The yield was calculated with the theoretical weight when all the polyester resin composition used in the depolymerization reaction was decomposed into BHET being 100%. When the yield is low, it is necessary to newly add petroleum raw materials to obtain the polyester resin composition by polycondensation, etc., which imposes an environmental burden. Therefore, it was evaluated according to the following criteria, and ◎ and ○ were regarded as passing. ◎: 90% or more ○: 80% or more △: Less than 80%.

[0071] (5) Detection method for compounds having 7 or more conjugated double bonds in the BHET composition The BHET composition was measured by high performance liquid chromatography (HPLC). HPLC was carried out by the following method. Apparatus: Ultimate 3000 (manufactured by Thermo Fisher Scientific) Column: Reverse phase column Mobile phase: A: 10 mmol / L ammonium acetate aqueous solution, B: acetonitrile Gradient conditions The content of the compound having 7 or more conjugated double bonds was calculated using the calibration curve prepared by HPLC.

[0072] (6) UV-Vis measurement of the BHET composition (color tone of the BHET composition) For the UV-Vis measurement of the BHET composition, a powdery BHET composition obtained by subjecting the BHET composition obtained through processes such as depolymerization and crystallization to vacuum drying at 70 °C under high vacuum for 8 hours or more was used. The measurement was carried out using a UV-1900i manufactured by Shimadzu Corporation. With a scanning wavelength range of 230 nm to 600 nm, a quartz cell (cell length: 1 cm) was used as the measurement cell, and absorbance was measured with a slit of 1 nm. For the sample solution, 50 mg of the BHET composition was taken into a 5 mL volumetric flask, 1 mL of N,N-dimethylformamide was added, and then the volume was made up with acetonitrile for preparation. The measurement was performed using the solution obtained by filtering the resulting sample solution through a PTFE filter (0.45 μm).

[0073] When the obtained absorbance was 0.3 or less, it was regarded as a BHET composition with little coloring. Also, by using a BHET composition with little coloring, the color tone of the resulting polyester resin composition becomes good.

[0074] (7) Amount of diethylene glycol in the polyester fiber composition (unit: parts by mass) Weigh 0.5 g of the polyester resin composition, use 1.3 ml of monoethanolamine containing 0.4 wt / vol% of 1,6-hexanediol, dissolve it at 260 °C, add methanol to the solution and cool it. Then, neutralize with terephthalic acid and measure the content of diethylene glycol (hereinafter referred to as DEG) by measuring the solution part with gas chromatography (GC-2025 manufactured by Shimadzu Corporation).

[0075] (8) Color tone of the polyester resin composition The polyester resin composition chip was measured as the Hunter value (b value) using a color difference meter (SM Color Computer model SM-T45 manufactured by Suga Test Instruments Co., Ltd.). The smaller this value, the less yellowing and the better the color tone.

[0076] (9) Haze value of the polyester resin composition (unit: %) Dissolve 2 g of the polyester resin composition chips in 20 ml of o-chlorophenol. Using a quartz cell with an optical path length of 20 mm and a haze meter (HGM-2DP type manufactured by Suga Test Instruments Co., Ltd.), measure the haze value of the solution by the integrating sphere type photoelectric photometry method. The smaller the haze value, the less turbidity and the better the quality.

[0077] (10) Heat resistance evaluation of the polyester film Cut out three pieces of the polyester film in a size of 5 cm × 5 cm, and perform a heat treatment at 230 °C for 30 minutes in the atmosphere using a hot air oven. Then, fold the three films in half with each other and check for cracks, and evaluate according to the following criteria. Note that ◎ and 〇 are regarded as passing. ◎: None of the three pieces cracked 〇: 1 to 2 pieces cracked △: All cracked.

[0078] (11) Color tone of the polyester film At an arbitrary point on the polyester film to be measured, cut out a sample with a size of 100 mm × 100 mm. Using a spectrophotometer CM-3600d manufactured by Konica Minolta, Inc., set the sample so that the angle between the normal of the film plane and the incident light is 0°. Measure the chromaticity b* at an arbitrary location on the sample under the target mask condition with a measuring diameter of φ25.4 mm by transmitted light. Then, move the sample so that it is more than 30 mm away from the center of the measurement location and repeat the same measurement 4 times (measurements were made at 5 arbitrary points). Evaluate the chromaticity b* according to the following criteria, and ◎ and ○ are regarded as passing. ◎: Less than 1.5 ○: 1.5 or more and less than 3.0 △: 3.0 or more.

[0079] (12) Transparency of the polyester film Transparency was evaluated by haze (%). The measurement of haze was carried out using a turbidity meter "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd. after leaving the polyester film standing 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 laminated polyester film. Regarding haze, evaluation was carried out according to the following criteria, and ◎ and ○ were regarded as passing. ◎: Less than 1.0 ○: 1.0 or more and less than 2.0 △: 2.0 or more.

[0080] (13) Spinnability of polyester fiber After vacuum drying the polyester resin composition at 150°C for 10 hours, it was supplied to an extruder, filtered at a spinning temperature of 293°C through a 15-micron nonwoven fabric filter with a diameter of 95 mm, and the molten polyester with a discharge rate of 70 g / min was discharged from a die nozzle having 96 round holes with a discharge hole diameter of 0.25 mm and a hole depth of 0.35 mm. The yarn after discharge was cooled and solidified with a cooling air of 0.5 m / sec by a cooling chimney, and an oil agent was applied while converging at a position 2 m below the die by an oiling device (coated with 1 mass% based on the fiber weight as pure oil content), and pre-interlacing was carried out using compressed air at an operating pressure of 0.25 MPa with an interlacing nozzle, and it was taken up by the first godet roll and the second godet roll with a peripheral speed of 2750 m / min to obtain a cheese package wound with 12 kg of an undrawn yarn of 130 dtex and 48 filaments. The peripheral speed of the winder was 2720 m / min. At this time, the number of yarn breaks (times / ton) was counted, evaluated according to the following criteria, and ◎ and 〇 were regarded as passing. ◎: 1.0 times / ton or less 〇: Greater than 1.0 times / ton and 1.5 times / ton or less △: Greater than 1.5 times / ton.

[0081] (Example 1) Step (a) 100 parts by mass of a used polyethylene terephthalate film for process release, 485 parts by mass of ethylene glycol, and 0.25 parts by mass of potassium hydroxide were charged into a reaction vessel, and depolymerization was carried out while gradually raising the temperature (190 - 230 °C). When the internal temperature reached 230 °C, the depolymerization was terminated, and it was allowed to cool to 25 °C. Solid-liquid separation was performed to obtain a depolymerized product containing impurities as a solid content.

[0082] Process (b) To the depolymerized product obtained in Process (a), 1000 parts by mass of water was added per 100 parts by mass of the used polyethylene terephthalate film for process release used, and it was dissolved at 100 °C to obtain Solution A.

[0083] Process (c) To Solution A, 10 parts by mass of Activated Carbon A was added per 100 parts by mass of the used polyethylene terephthalate film for process release used, and it was stirred while heating. After 60 minutes, Activated Carbon A was removed using a 1.0 μm filter to obtain Solution B.

[0084] Process (d) Solution B was cooled to crystallize the BHET composition, and crystals of the wetted BHET composition were obtained as solids by filtration using a No. 5B filter paper. The obtained crystals of the wetted BHET composition were dried to obtain the BHET composition.

[0085] The properties of the obtained BHET composition are shown in Table 1. The obtained BHET composition had a good yield and was a high-quality BHET composition.

[0086] The obtained BHET composition was subjected to a polycondensation reaction by the method shown below to obtain a polyester resin composition, and evaluation was carried out.

[0087] The entire amount of the BHET composition obtained by the depolymerization reaction was added to the polymerization reaction tank. When it was melted at 200°C, 0.01 wt% was added as the addition amount when the polyester resin composition obtained by antimony trioxide as the polycondensation reaction catalyst was 100 wt%. After that, while gradually raising the temperature inside the apparatus to 290°C, the pressure inside the apparatus was reduced to 1 Torr or less. As the polymerization reaction proceeded, the viscosity of the reaction product increased, and the reaction was terminated when the increase value of the stirring torque of the reaction product reached the polymerization end target value. The polyester was discharged from the polymerization reaction tank to the water tank. The discharged polyester was rapidly cooled in the water tank and chipped with a cutter to obtain a polyester resin composition.

[0088] The properties of the obtained polyester resin composition are shown in Table 1. The obtained polyester resin composition had good DEG content, color tone b value, and solution haze.

[0089] Also, a polyester film was obtained by the method shown below using the obtained polyester resin composition, and evaluation was carried out.

[0090] As the resin constituting the first layer and the third layer, 90 parts by weight of the polyester resin composition obtained in Example 1 and 10 parts by weight of virgin PET were blended, dried under reduced pressure at 160 °C for 2 hours, and then charged into an extruder for the first layer and the third layer. Further, as the resin constituting the second layer, 80 parts by weight of the polyester resin composition obtained in Example 1 and 20 parts by weight of virgin PET were blended, dried under reduced pressure at 160 °C for 2 hours, and then charged into an extruder for the second layer. Each raw material was melted at 280 °C in the extruder, merged and laminated with a lamination merging block, and laminated in three layers in the order of the first layer, the second layer, and the third layer. Then, it was co-extruded onto a casting drum with a surface temperature of 25 °C from a die, and adhered, cooled, and solidified by static electricity to create a laminated unstretched sheet having a three-layer structure. Subsequently, the sheet was preheated with a group of heated rolls, then stretched 3.3 times in the longitudinal direction (the vertical direction, that is, the advancing direction of the sheet) at a temperature of 90 °C, and then cooled with a group of rolls at 25 °C to obtain a uniaxially stretched film. While gripping both ends of the obtained uniaxially stretched film with clips, it was stretched 3.5 times in the direction perpendicular to the longitudinal direction (the width direction) in a heating zone at 110 °C in a tenter. Subsequently, heat setting was performed at a temperature of 230 °C for 10 seconds in a heat treatment zone in the tenter. Next, after gradually cooling uniformly in a cooling zone, both end portions of the film gripped by the tenter clips were cut off, and this was wound up to obtain a polyester film with a thickness of 25 μm.

[0091] The obtained polyester film had good heat resistance, color tone, and transparency.

[0092] Also, polyester fibers were obtained by the method shown below using the obtained polyester resin composition, and evaluation was performed.

[0093] The obtained polyester resin composition was dried under reduced pressure at 150 °C for 10 hours and then charged into an extruder. At a spinning temperature of 293 °C, the molten polyester was filtered through a 15-micron nonwoven fabric filter with a diameter of 95 mm and discharged at a discharge rate of 70 g / min from a spinneret nozzle having 95 round holes with a discharge hole diameter of 0.25 mm and a hole depth of 0.35 mm. The extruded yarn was cooled and solidified by a cooling chimney with a cooling air flow rate of 0.5 m / s, and an oil agent was applied while converging with an oiling device at a position 2 m below the spinneret (coated at 1% by weight based on the fiber weight as pure oil content). Preliminary texturing was performed using compressed air with an operating pressure of 0.25 MPa at an interlacing nozzle, and the yarn was taken up by a first godet roll and a second godet roll with a peripheral speed of 2750 m / min to obtain a cheese package wound with 12 kg of 130 dtex, 48-filament undrawn yarn. The peripheral speed of the winder was 2720 m / min.

[0094] The number of yarn breaks at this time was 0.7 times / ton, and the yarn manufacturing property was good.

[0095] (Examples 2 to 5, Comparative Examples 1 to 2) BHET compositions, polyester resin compositions, polyester films, and polyester fibers were obtained in the same manner as in Example 1, except that the amount of water added in step (b) was changed as shown in Table 1.

[0096] The BHET compositions obtained in Examples 2 and 3 had good yields and good quality. The polyester resin compositions obtained in Examples 2 and 3 had good DEG content, color tone b value, and solution haze. The polyester films obtained in Examples 2 and 3 had good heat resistance, color tone, and transparency. The polyester fibers obtained in Examples 2 and 3 had good yarn manufacturing properties.

[0097] The BHET compositions obtained in Examples 4 and 5 had good yields but were slightly yellowish BHET compositions. The polyester resin compositions obtained in Examples 4 and 5 had good DEG contents and solution haze although their b color values were slightly high. The polyester films obtained in Examples 4 and 5 had good heat resistance and transparency although their color tones deteriorated slightly. The polyester fibers obtained in Examples 4 and 5 had good spinning properties.

[0098] The BHET composition obtained in Comparative Example 1 had a slightly low yield and was a strongly yellowish BHET composition. The polyester resin composition obtained in Comparative Example 1 had slightly high DEG content and solution haze and a high b color value. The polyester film obtained in Comparative Example 1 had slightly low heat resistance, deteriorated color tone, and slightly low transparency. The polyester fiber obtained in Comparative Example 1 had slightly low spinning properties.

[0099] The BHET composition obtained in Comparative Example 2 had a good yield but was a strongly yellowish BHET composition. The polyester resin composition obtained in Comparative Example 2 had good DEG content and solution haze although its b color value was high. The color tone of the polyester film obtained in Comparative Example 2 deteriorated. The polyester fiber obtained in Comparative Example 2 had good spinning properties.

[0100]

Table 1

[0101] (Examples 6 - 8, Comparative Examples 3 - 5) BHET compositions, polyester resin compositions, polyester films, and polyester fibers were obtained in the same manner as in Example 1 except that the type of solvent used in step (b) was changed.

[0102] The BHET compositions obtained in Examples 6 to 8 were BHET compositions with good yields and good quality. The polyester resin compositions obtained in Examples 6 to 8 had good amounts of DEG, b values of color tone, and solution haze. The polyester films obtained in Examples 6 to 8 had good heat resistance, color tone, and transparency. The polyester fibers obtained in Examples 6 to 8 had good spinning performance.

[0103] The BHET composition obtained in Comparative Example 3 had a poor yield. The polyester resin composition obtained in Comparative Example 3 had a large amount of DEG and a slightly high b value of color tone, but the solution haze was good. The polyester film obtained in Comparative Example 3 had low heat resistance and a slightly deteriorated color tone. The polyester fiber obtained in Comparative Example 3 had poor spinning performance.

[0104] The BHET compositions obtained in Comparative Examples 4 and 5 had poor yields. The polyester resin compositions obtained in Comparative Examples 4 and 5 had a slightly large amount of DEG and a slightly high b value of color tone. The polyester films obtained in Comparative Examples 4 and 5 had low heat resistance and a slightly deteriorated color tone. The polyester fibers obtained in Comparative Examples 4 and 5 had poor spinning performance.

[0105]

Table 2

[0106] (Examples 9 to 12, Comparative Examples 6 to 9) BHET compositions, polyester resin compositions, polyester films, and polyester fibers were obtained in the same manner as in Example 1 except that the type of adsorbent added in step (c) was changed.

[0107] The BHET composition obtained in Example 9 was a BHET composition with a good yield and good quality. The polyester resin composition obtained in Example 9 had good amounts of DEG, b values of color tone, and solution haze. The polyester film obtained in Example 9 had good heat resistance, color tone, and transparency. The polyester fiber obtained in Example 9 had good spinning performance.

[0108] The BHET composition obtained in Example 10 was a BHET composition with a good yield but slightly yellowish. The polyester resin composition obtained in Example 10 had a slightly high b value of color tone, but the DEG content and solution haze were good. The polyester film obtained in Example 10 had slightly deteriorated color tone, but its heat resistance and transparency were good. The polyester fiber obtained in Example 10 had good spinning performance.

[0109] The BHET composition obtained in Example 11 was a BHET composition with a good yield but slightly yellowish. The polyester resin composition obtained in Example 11 had a slightly high DEG content and a slightly high b value of color tone. The polyester film obtained in Example 11 had slightly low heat resistance and slightly deteriorated color tone. The polyester fiber obtained in Example 11 had slightly low spinning performance.

[0110] The BHET composition obtained in Example 12 was a BHET composition with a good yield and good quality. The polyester resin composition obtained in Example 12 had a slightly high DEG content, but the b value of color tone and solution haze were good. The polyester film obtained in Example 12 had slightly low heat resistance, but its color tone and transparency were good. The polyester fiber obtained in Example 12 had slightly low spinning performance.

[0111] The BHET composition obtained in Comparative Example 6 had strong yellowing but a good yield. The polyester resin composition obtained in Comparative Example 6 had a poor b value of color tone. The polyester film obtained in Comparative Example 6 had deteriorated color tone, but its heat resistance and transparency were good. The polyester fiber obtained in Comparative Example 6 had good spinning performance.

[0112] The polyester resin composition obtained in Comparative Example 7 had a high DEG content and low heat resistance. The polyester fiber obtained in Comparative Example 7 had poor spinning performance.

[0113] The BHET composition obtained in Comparative Example 8 had a strong yellow tint. The polyester resin composition obtained in Comparative Example 8 had a poor b value of color tone. The color tone of the polyester film obtained in Comparative Example 8 deteriorated.

[0114] The BHET composition obtained in Comparative Example 9 was a BHET composition with a slightly yellow tint. The polyester resin composition obtained in Comparative Example 9 had a large amount of DEG and a slightly high b value of color tone. The polyester film obtained in Comparative Example 9 had low heat resistance and a slightly deteriorated color tone. The polyester fiber obtained in Comparative Example 9 had poor spinning performance.

[0115]

Table 3

[0116] (Examples 13 to 15, Comparative Example 10) Except for changing the amount of the adsorbent used in step (c), BHET composition, polyester resin composition, polyester film, and polyester fiber were obtained in the same manner as in Example 1.

[0117] The BHET composition obtained in Example 13 had a good yield but was a BHET composition with a slightly yellow tint. The polyester resin composition obtained in Example 13 had a slightly high b value of color tone, but the amount of DEG and solution haze were good. The polyester film obtained in Example 13 had a slightly deteriorated color tone, but the heat resistance and transparency were good. The polyester fiber obtained in Example 13 had good spinning performance.

[0118] The BHET compositions obtained in Examples 14 and 15 had good yields and good quality. The polyester resin compositions obtained in Examples 14 and 15 had good amounts of DEG, b values of color tone, and solution haze. The polyester films obtained in Examples 14 and 15 had good heat resistance, color tone, and transparency. The polyester fibers obtained in Examples 14 and 15 had good spinning performance.

[0119] The BHET composition obtained in Comparative Example 10 had a poor yield.

[0120]

Table 4

[0121] Table 5 shows the average pore diameter, pH, and oxygen element composition measured by XPS of the adsorbent used in step (c).

[0122]

Table 5

Industrial Applicability

[0123] The thus-obtained BHET composition, polyester resin composition, polyester film, and polyester fiber are useful as optical materials, agricultural materials, horticultural materials, fishery materials, civil engineering and construction materials, stationery, medical supplies, automotive parts, electrical and electronic parts, clothing fibers, or other applications.

Claims

1. A method for producing a bis-(2-hydroxyethyl) terephthalate composition, comprising steps (a) to (d), the steps satisfying the conditions (i) to (iii). (a) A step of depolymerizing a polyester resin composition. (b) A step of adding a solvent to the depolymerized product to dissolve it, thereby obtaining solution A. (c) contacting solution A with an adsorbent to obtain solution B. (d) A step of obtaining a bis-(2-hydroxyethyl) terephthalate composition from solution B. (i) The amount of the solvent added in the step (b) is 20 parts by mass or more and 7,000 parts by mass or less based on 100 parts by mass of the polyester resin composition. (ii) The solvent in step (b) contains 90 parts by mass or more of water relative to 100 parts by mass of the solvent. (iii) The average pore size of the adsorbent is 0.5 nm or more and 200 nm or less.

2. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the amount of ethylene glycol is 10 parts by mass or less per 100 parts by mass of the solvent in step (b).

3. 2. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the adsorbent is at least one of activated carbon, zeolite, and silica gel.

4. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the pH of the adsorbent is 2 or more and 9 or less.

5. 2. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the elemental composition of oxygen in the adsorbent is 1 atomic % or more and 70 atomic % or less when the adsorbent is subjected to XPS measurement.

6. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the content of the compound having 7 or more conjugated double bonds in the obtained bis-(2-hydroxyethyl) terephthalate composition is 0.01 ppm by mass or more and 10 ppm by mass or less.

7. The method for producing a bis-(2-hydroxyethyl) terephthalate composition according to claim 1, wherein the bis-(2-hydroxyethyl) terephthalate composition has an absorbance at 330 nm of 0.3 or less when subjected to UV-Vis measurement.

8. A polyester resin composition obtained by polycondensing the bis-(2-hydroxyethyl) terephthalate composition according to claim 1.

9. The polyester resin composition according to claim 8, wherein the diethylene glycol content is 2 parts by mass or less.

10. A polyester film comprising the polyester resin composition according to claim 9.

11. A fiber comprising the polyester resin composition according to claim 9.

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