TW202413511A - Chemically recycled polyethylene terephthalate resin, molded body of same, and method for producing chemically recycled polyethylene terephthalate resin - Google Patents

Abstract

The present invention addresses the problem of providing a chemically recycled polyethylene terephthalate resin which includes only a few foreign substances that are difficult to remove by a filter. A chemically recycled polyethylene terephthalate resin according to the present invention is characterized by satisfying the requirements (1) and (2) described below. (1) Aluminum atoms and phosphorus atoms are contained. (2) The amount of foreign substances having a particle diameter of 0.50 [mu]m to 0.69 [mu]m as determined by a particle counter is 2,000 per ml or less.

Description

Chemically recycled polyethylene terephthalate resin and its molded body, and method for producing chemically recycled polyethylene terephthalate resin

The present invention relates to chemically recycled polyethylene terephthalate resin and its molded body, and a method for producing chemically recycled polyethylene terephthalate resin.

Polyester resins are widely used for packaging and industrial components because of their excellent mechanical strength, chemical stability, heat resistance, moisture resistance, high transparency, and stable supply at low prices.

As a general-purpose polyester resin, there is polyethylene terephthalate, which is a condensation product of terephthalic acid and ethylene glycol. Terephthalic acid and ethylene glycol are produced from petroleum, which is a fossil fuel. In recent years, in order to reduce carbon dioxide emissions and other environmental burdens, the recycling of products derived from fossil fuels has been moving towards. For polyester, not only physical recycling of crushing products and remelting them into shapes, but also chemical recycling of decomposing polyester to monomer levels and using them as raw materials for further condensation has gradually become practical.

In order to reduce the environmental burden on polyester resins, the use of polyethylene terephthalate obtained by chemical recycling from plastic bottles for beverages and polyester fibers for clothing is also being studied. Even such resins that deal with environmental burdens are required to be used for the same purposes as non-recycled resins and have the same properties.

When polyester resin is used as film, fiber, or beverage bottle, if there are a lot of foreign matter in the resin, the workability may be deteriorated during processing due to film rupture, fiber breakage, etc., resulting in a decrease in product yield, or the foreign matter may remain in the product as a defect, resulting in poor quality. In addition, when used as a raw material for hollow molded products, it is difficult to obtain a hollow molded body with excellent transparency.

As for the generation of foreign matter, it is known that metal catalysts are modified and insoluble in resin, thereby becoming foreign matter. Antimony, germanium compounds, and titanium compounds have been widely used as polyester polycondensation catalysts used in the polycondensation of polyester. Antimony trioxide is a cheap catalyst with excellent catalytic activity. If it is used as the main component, that is, in an amount that can achieve a practical polymerization rate, metal antimony will precipitate during polycondensation, thereby generating black stains and foreign matter in polyester and causing film surface defects.

As a condensation catalyst for reducing the amount of foreign matter, a catalyst system composed of an aluminum compound and a phosphorus compound has been disclosed (for example, see Patent Document 1). In addition, a technique is known that deeply studies the preparation method of an ethylene glycol solution of an aluminum compound and a phosphorus compound used as a catalyst, and reduces foreign matter generated by the condensation catalyst by adding a phosphorus compound after the ester reaction is completed (for example, see Patent Documents 2 and 3). [Prior Technical Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Publication No. 2007-204557 [Patent Document 2] WO2005/075539 [Patent Document 3] Japanese Patent Publication No. 2005-187558

[Problems to be solved by the invention]

However, it has been found that in the catalyst system composed of the above-mentioned aluminum compound and phosphorus compound, there is also a problem that foreign matter in the catalyst is generated which is difficult to remove by a filter.

The present invention is completed based on the subject of the prior art, and its purpose is to synthesize chemically recycled polyethylene terephthalate resin from raw materials obtained by chemical recycling, and use aluminum compounds and phosphorus compounds as catalysts during polymerization, thereby providing a chemically recycled polyethylene terephthalate resin with less foreign matter (specifically foreign matter with a particle size of 0.5 to 0.69 μm) that is difficult to remove by a filter. [Means for solving the problem]

The inventors of this case have repeatedly studied the polycondensation of raw materials including chemically recycled bis-2-hydroxyethyl terephthalate, and found that by using chemically recycled bis-2-hydroxyethyl terephthalate and using aluminum compounds and phosphorus compounds as catalysts during polymerization, the foreign matter (especially foreign matter that is difficult to remove by filters) in the chemically recycled polyethylene terephthalate resin can be reduced compared to the polyethylene terephthalate resin obtained from virgin terephthalic acid and virgin ethylene glycol raw materials.

That is, the present invention is composed of the following. [1] A chemically recycled polyethylene terephthalate resin, characterized by satisfying the following (1) to (2). (1) Containing aluminum atoms and phosphorus atoms (2) The amount of foreign matter with a particle size of 0.50 to 0.69 μm obtained by a particle counter is 2000 or less/ml [2] The chemically recycled polyethylene terephthalate resin as described in [1] above, wherein the content of the aluminum atoms in the chemically recycled polyethylene terephthalate resin is 50 mass ppm or less, and the content of the phosphorus atoms in the chemically recycled polyethylene terephthalate resin is 100 mass ppm or less. [3] The chemically recycled polyethylene terephthalate resin as described in [1] or [2] above, wherein the intrinsic viscosity retention rate is 89% or more. [4] A chemically recycled polyethylene terephthalate resin as described in any one of [1] to [3] above, wherein the color b value is 10 or less. [5] A molded article comprising the chemically recycled polyethylene terephthalate resin as described in any one of [1] to [4] above. [6] A method for producing a chemically recycled polyethylene terephthalate resin, which is a method for producing a polyethylene terephthalate resin using a raw material comprising chemically recycled bis-2-hydroxyethyl terephthalate obtained by decomposing a polyester resin, wherein the raw material comprising chemically recycled bis-2-hydroxyethyl terephthalate is subjected to a condensation reaction directly or after its OH terminal is esterified in the presence of an aluminum compound and a phosphorus compound. [7] A method for producing a chemically recycled polyethylene terephthalate resin as described in [6] above, wherein the amount of free ethylene glycol components in 100 mol% of all polyol components constituting the chemically recycled bis-2-hydroxyethyl terephthalate is 1.5 mol% or less. [Effect of the invention]

By using a raw material including chemically recycled bis-2-hydroxyethyl terephthalate and using an aluminum compound and a phosphorus compound as a catalyst during polymerization, a chemically recycled polyethylene terephthalate resin having less foreign matter (especially foreign matter that is difficult to remove by a filter) can be formed compared to a polyethylene terephthalate resin obtained from virgin terephthalic acid and virgin ethylene glycol raw materials. Therefore, the chemically recycled polyethylene terephthalate resin of the present invention can be ideally used as a material for various molded products such as films, fibers, beverage bottles, and optical applications.

The chemically recycled polyethylene terephthalate resin of the present invention preferably has high transparency. Also, it preferably has suppressed coloring. Furthermore, it preferably has a high degree of thermal stability. The resin having high transparency, suppressed coloring and high degree of thermal stability is particularly suitable as a material for various molded products such as films, fibers, beverage bottles, and optical applications.

The method for producing chemically recovered polyethylene terephthalate resin of the present invention is characterized in that bis-2-hydroxyethyl terephthalate obtained by chemical recovery is polycondensed. In addition, bis-2-hydroxyethyl terephthalate is sometimes referred to as BHET, and bis-2-hydroxyethyl terephthalate obtained by chemical recovery is sometimes referred to as chemically recovered BHET or CR-BHET.

Also, polyethylene terephthalate resin obtained by polycondensing chemically recycled BHET is sometimes referred to as chemically recycled PET or CR-PET. Also, polyethylene terephthalate is sometimes referred to as PET.

The chemically recycled PET resin of this embodiment can be used as a chemically recycled PET resin with a small amount of foreign matter with a particle size of 0.50~0.69μm. The inventors of this case repeatedly studied the polymerization of chemically recycled PET using chemically recycled BHET obtained by decomposing polyester resin as a raw material, and found that the content of free ethylene glycol in the oligomer reaction liquid obtained by chemically recycled BHET is small. On the other hand, in the oligomer reaction liquid obtained by esterifying terephthalic acid and ethylene glycol, a large amount of free ethylene glycol exists. If a polymerization catalyst is added thereto and polymerization is carried out, it is found that in the generated resin, foreign matter derived from the catalyst that is difficult to remove by a filter increases.

The reason for this can be inferred as follows. If a polymerization catalyst is added to an oligomer reaction liquid in which a large amount of free ethylene glycol exists, and the internal temperature is made to be higher than the boiling point of ethylene glycol, ethylene glycol will rapidly evaporate. Because of its rapid volatility and large amount of volatility, it exerts certain effects on the catalyst and promotes the modification of the catalyst. As a result, foreign matters derived from the catalyst increase in the generated resin. In order to suppress the increase of this foreign matter, it is important to suppress the free ethylene glycol content at the time of adding the polymerization catalyst. At the time of adding the polymerization catalyst, the oligomer reaction liquid containing BHET obtained from chemically recovered BHET has a lower content of free ethylene glycol than the oligomer reaction liquid obtained from terephthalic acid and ethylene glycol. Therefore, at the time of adding the polymerization catalyst, the volatility of ethylene glycol can be reduced and the volatility can be reduced, thereby reducing the effect on the catalyst, inhibiting the modification of the catalyst, and reducing the foreign matter derived from the catalyst in the generated resin. It is also inferred that by using aluminum compounds and phosphorus compounds as catalysts, foreign matter in chemically recovered PET can be reduced.

(Chemically recycled BHET) Chemically recycled BHET is obtained by heating PET resin in the presence of ethylene glycol to depolymerize it. The PET resin used as the source is preferably one that has passed through users in any form. Examples thereof include: containers such as plastic bottles and pallets collected from the roadside, fibers, products, waste products before becoming products during manufacturing, products that cannot be shipped to the market as inferior products, ends clamped during film stretching, cut ends, and molded products returned due to customer complaints, etc. Among these PET resins used as the source, terephthalic acid and ethylene glycol can be derived from petroleum or biomass. It can also be a molded product that is physically recycled. It can also be a mixture of these PET resins.

The PET resin used as the source is generally used in the depolymerization step after being crushed, washed, and foreign matter is removed. During the depolymerization, ethylene glycol, sodium hydroxide, potassium hydroxide, and other alkaline compounds are added to the PET resin and heated to depolymerize. The resulting reactant is filtered and decolorized for solids as required, and then the remaining ethylene glycol is distilled off to form a crude BHET product. The crude BHET is purified by distillation, crystallization, etc., thereby forming chemically recovered BHET of a purity for polycondensation.

In addition, as mentioned above, the "chemically recovered BHET" in the present invention refers to the one obtained by depolymerizing PET resin, and may also contain components other than BHET as impurities. Specifically, the chemically recovered BHET may also include BHET, a dicarboxylic acid diester composed of one molecule of a polycarboxylic acid component such as bis-2-hydroxyethyl isophthalate and two molecules of a polyol component; a linear dimer of the carboxylic acid diester and its polymers thereof; a carboxylic acid monoester composed of one molecule of a polycarboxylic acid component such as mono-2-hydroxyethyl terephthalate and one molecule of a polyol component; free polycarboxylic acids such as free terephthalic acid; free polyols such as free ethylene glycol, etc. The chemically recovered BHET contains BHET as a main component, preferably containing 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of BHET.

The acid value and hydroxyl value of chemically recovered BHET are preferably 6500 eq/ton or more, more preferably 7000 eq/ton or more, and even more preferably 7500 eq/ton or more. The upper limit is preferably 9500 eq/ton, more preferably 9000 eq/ton, and even more preferably 8500 eq/ton. That is, the acid value and hydroxyl value of chemically recovered BHET are preferably 6500 to 9500 eq/ton, more preferably 7000 to 9000 eq/ton, and even more preferably 7500 to 8500 eq/ton. By being within the above range, sufficient purity can be maintained on the one hand, and productivity can be ensured on the other hand. In addition, the acid value 1eq/ton means that 1 mol of carboxylic acid group (-COOH) is contained per ton of the object (here, chemically recovered BHET), and the hydroxyl value 1eq/ton means that 1 mol of OH group is contained per ton of the object (here, chemically recovered BHET). The same meaning applies to the case where the acid value and hydroxyl value are specified in other objects (oligomers, resins, etc.).

As described above, chemically recovered BHET may also contain polycarboxylic acid components other than terephthalic acid components and polyol components other than ethylene glycol. Examples of polycarboxylic acid components other than terephthalic acid components include isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, adipic acid, sebacic acid, and cyclohexane dicarboxylic acid. Examples of polyol components other than ethylene glycol include diethylene glycol, neopentyl glycol, cyclohexanedimethanol, trimethylene glycol, tetramethylene glycol, ethylene glycol or propylene glycol adducts of bisphenol A, and ethylene glycol or propylene glycol adducts of bisphenol S. Chemically recovered BHET may contain one or more polycarboxylic acid components, and may contain one or more polyol components.

The amount of terephthalic acid component contained in the chemically recovered BHET is preferably 98.0 mol % or more (or more), more preferably 98.3 mol % or more, further preferably 98.5 mol % or more, further preferably 98.8 mol % or more, particularly preferably 99.0 mol % or more, and most preferably 99.2 mol % or more, when all polycarboxylic acid components in the chemically recovered BHET are set to 100 mol %.

As mentioned above, chemically recovered BHET is preferably obtained by depolymerizing PET resin containing recycled products from the market. In order to adjust the crystallinity, physical properties, etc., recycled PET from the market sometimes adds components other than PET. It is not cost-effective to select only pure PET from the recycled products or to purify BHET to a level where acid components other than terephthalic acid cannot be detected. Therefore, the amount of terephthalic acid contained in chemically recovered BHET is preferably 99.98 mol% or less, more preferably 99.95 mol% or less, and can also be 99.9 mol% or less, 99.85 mol% or less, or 99.8 mol% or less, when all polycarboxylic acid components of chemically recovered BHET are set to 100 mol%. That is, the amount of terephthalic acid contained in the chemically recovered BHET is preferably 98.0-99.98 mol%, more preferably 98.3-99.95 mol%, and even more preferably 98.5-99.95 mol%, and may also be 98.8-99.9 mol%, 99.0-99.85 mol%, or 99.2-99.8 mol%, when all polycarboxylic acid components in the chemically recovered BHET are set to 100 mol%.

In many cases, isophthalic acid is contained as a polycarboxylic acid component other than the terephthalic acid component contained in the chemically recovered BHET. The content of the isophthalic acid component is preferably 2.0 mol% or less (or less than), then preferably 1.7 mol% or less, more preferably 1.5 mol% or less, more preferably 1.2 mol% or less, particularly preferably 1.0 mol% or less, and most preferably 0.8 mol% or less. In addition, the content of the isophthalic acid component may be 0.15 mol% or less or less than 0.15 mol%. The content of the isophthalic acid component is preferably 0.02 mol% or more, more preferably 0.05 mol% or more, and may also be 0.1 mol% or more, 0.15 mol% or more, or 0.2 mol% or more. That is, the content of the isophthalic acid component is preferably 0.02-2.0 mol%, more preferably 0.02-1.7 mol%, and even more preferably 0.05-1.5 mol%. It can also be 0.1-1.2 mol%, 0.15-1.0 mol%, 0.2-0.8 mol%, or 0.02 mol% or more but less than 0.15 mol%.

The amount of ethylene glycol contained in the chemically recovered BHET is preferably 98.7 mol% or more, more preferably 99.0 mol% or more, and may also be 99.2 mol% or more, 99.3 mol% or more, or 99.4 mol% or more, when all polyol components of the chemically recovered BHET are set to 100 mol%. The amount of ethylene glycol component may also be 98.0 mol% or more, 98.3 mol% or more, 98.6 mol% or more, or 98.8 mol% or more.

The amount of free ethylene glycol in the ethylene glycol component contained in the chemically recovered BHET is preferably 1.5 mol% or less, more preferably 1.3 mol% or less, further preferably 1.2 mol% or less, further preferably 1.0 mol% or less, particularly preferably 0.8 mol% or less, and most preferably 0.6 mol% or less, when all polyol components of the chemically recovered BHET are set to 100 mol%. In this case, the free ethylene glycol content in the oligomer reaction solution obtained from the chemically recovered BHET is reduced, and the amount of foreign matter in the obtained resin that is difficult to remove by a filter can be further suppressed.

As mentioned above, it is not cost-effective to select pure PET from the recycled materials from the market or to purify BHET to a level where polyol components other than ethylene glycol are not detected. In addition, diethylene glycol is produced as a side reaction in the production step of PET, and it is difficult to avoid its generation. Therefore, among all the polyol components of chemically recovered BHET, the amount of ethylene glycol is preferably 99.9 mol% or less, more preferably 99.8 mol% or less, more preferably 99.75 mol% or less, and particularly preferably 99.7 mol% or less. That is, the amount of ethylene glycol is preferably 98.0~99.9 mol%, more preferably 98.3~99.8 mol%, more preferably 98.6~99.75 mol%, and more preferably 98.8~99.7 mol%.

Among the polyol components other than ethylene glycol contained in chemically recovered BHET, most of them contain diethylene glycol components. The content of diethylene glycol components, when all polyol components of chemically recovered BHET are set to 100 mol%, is preferably 2.0 mol% or less, more preferably 1.7 mol% or less, more preferably 1.4 mol% or less, and particularly preferably 1.2 mol% or less. The content of the diethylene glycol component is preferably 0.1 mol% or more, more preferably 0.3 mol% or more, more preferably 0.5 mol% or more, and particularly preferably 0.6 mol% or more. That is, the content of the diethylene glycol component is preferably 0.1~2.0 mol%, more preferably 0.3~1.7 mol%, more preferably 0.5~1.4 mol%, and particularly preferably 0.6~1.2 mol%.

The above-mentioned polycarboxylic acid components such as terephthalic acid components and isophthalic acid components, and polyol components such as ethylene glycol components and diethylene glycol components also include values existing as monomers (that is, one molecule of the compound is free) in the chemically recovered BHET.

In order to reduce the amount of diethylene glycol contained in chemically recovered BHET, it is also better to appropriately adjust the amount and time of added ethylene glycol during the depolymerization of PET. If the amount of ethylene glycol is small, sufficient ester exchange with diethylene glycol in PET may not occur. On the other hand, if the amount of ethylene glycol is too much, diethylene glycol may be generated from ethylene glycol and mixed with chemically recovered BHET. The amount of ethylene glycol added should be 5 to 7 times the mass of PET. If the depolymerization time is short, sufficient ester exchange with diethylene glycol in PET may not occur. If the time is long, diethylene glycol may be generated from ethylene glycol and mixed with chemically recovered BHET. The depolymerization time should be 3 to 10 hours. In order to complete the depolymerization in an appropriate time, the PET resin should be crushed into an appropriate size in advance. In order to further reduce the amount of diethylene glycol in the chemically recovered BHET, recrystallization is preferably performed.

In chemically recycled BHET, the PET resin used as the source may not be uniform, and the amount of copolymer components is not always the same. In addition, it is difficult to completely avoid the generation of diethylene glycol in the production of PET resin, and the amount of diethylene glycol generated varies depending on the different production conditions and equipment conditions. Due to these main reasons, the composition of the obtained PET resin will change. If it exceeds a certain range, there is a concern that the resin properties of the chemically recycled PET resin will be reduced. In order to obtain molded products with stable quality from chemically recycled PET resin, it is advisable to make the copolymer components of the chemically recycled PET resin within a specific range, to expand the selection range of the production conditions of the chemically recycled PET resin, and to obtain the chemically recycled PET resin with good productivity, it is advisable to make the polycarboxylic acid component and polyol component of the chemically recycled BHET within a certain range.

For example, in the case of plastic bottles, a small amount of isophthalic acid and diethylene glycol are often copolymerized in PET resin. In order to ensure that the composition of chemically recycled BHET used in the manufacture of chemically recycled PET is within the above range, it is not only necessary to select chemically recycled BHET based on the above criteria, but it is also advisable to adjust the proportion of PET resin used as the source for depolymerization, mix multiple chemically recycled BHET to meet the above range, or appropriately purify the chemically recycled BHET, so as to adjust it to the range of (e), (f), and (g) for selection.

(e) The amount of terephthalic acid component is 98.0 mol% to 99.98 mol% relative to all polycarboxylic acid components in chemically recovered bis-2-hydroxyethyl terephthalate (f) The amount of ethylene glycol component is 98.0 mol% to 99.9 mol% (preferably 98.7 mol% to 99.9 mol%) relative to all polyol components in chemically recovered bis-2-hydroxyethyl terephthalate (g) The amount of diethylene glycol component is 0.1 mol% to 2.0 mol% relative to all polyol components in chemically recovered bis-2-hydroxyethyl terephthalate

Furthermore, it is preferable to make it within the range of (h). (h) The amount of isophthalic acid component is 0.02 mol% or more and 2.0 mol% or less relative to all polycarboxylic acid components in chemically recovered bis-2-hydroxyethyl terephthalate

In order to reduce the amount of free ethylene glycol contained in chemically recovered BHET, the ethylene glycol solution of crude BHET obtained by chemical recovery is appropriately purified by a purification step and adjusted to within the range of (i). Alternatively, multiple chemically recovered BHETs may be mixed and adjusted to within the range of (i). (i) The amount of free ethylene glycol components is 1.5 mol% or less relative to all polyol components in chemically recovered bis-2-hydroxyethyl terephthalate

In addition, copolymerized polyol components such as diethylene glycol have a higher boiling point than ethylene glycol and are not easily volatile during polycondensation, so they are easily incorporated into polyester resins. It is advisable to consider these factors to determine the range of the amount of polyol components other than ethylene glycol. When the amount of terephthalic acid component relative to 100 mol% of all polycarboxylic acid components in the above-mentioned chemically recovered bis-2-hydroxyethyl terephthalate is set as TPA(b) mol%, and the amount of ethylene glycol component relative to 100 mol% of all polyol components in the chemically recovered bis-2-hydroxyethyl terephthalate is set as EG(b) mol%, the upper limit of the value of (100-TPA(b))+(100-EG(b))×2 is preferably 4 mol%, more preferably 3.5 mol, further preferably 3 mol, and particularly preferably 2.8 mol. The lower limit of the value of (100-TPA(b))+(100-EG(b))×2 is preferably 0.15 mol%, more preferably 0.3 mol%, and even more preferably 0.5 mol%. That is, the value of (100-TPA(b))+(100-EG(b))×2 is preferably 0.15~4 mol%, more preferably 0.3~3.5 mol%, even more preferably 0.5~3 mol%, and particularly preferably 0.5~2.8 mol%. By making it within the above range, the thermal stability of the obtained chemically recycled PET resin can also be maintained to a high degree. Furthermore, the selection range of the manufacturing conditions of chemically recycled PET can be expanded, and chemically recycled PET can be obtained with good productivity.

Chemically recycled BHET sometimes contains polymerization catalysts from the PET resin as a source, and sometimes also acts as a catalyst during the polycondensation reaction of producing chemically recycled PET from chemically recycled BHET. Chemically recycled BHET preferably does not contain polymerization catalysts from the PET resin as a source or contains them at a level that is not detectable. Chemically recycled BHET preferably uses BHET purified to a level where metal components derived from the polymerization catalyst are not detected by the purification step.

(Method for producing chemically recycled PET resin) The method for producing chemically recycled PET resin of the present invention can be carried out by a method having known steps, except that chemically recycled BHET obtained by decomposing polyester resin is used as a raw material, and a polyester polymerization catalyst composed of an aluminum compound and a phosphorus compound is used as a catalyst.

The method for producing chemically recycled PET resin of the present invention comprises the following steps: directly polycondensing the raw material including the recycled BHET obtained by decomposing the polyester resin, or polycondensing after esterifying and/or transesterifying the OH terminal thereof. Specifically, it is preferable to have: the first step of adding chemically recycled BHET to a reaction vessel and melting it, or adding chemically recycled BHET and copolymerization components according to needs to a reaction vessel and melting it, and then esterifying the OH terminal of the chemically recycled BHET; and the second step of further adding an aluminum compound and a phosphorus compound to the reactant obtained in the first step to carry out a polycondensation reaction. The second step is preferably carried out under reduced pressure while removing the generated diol to the outside of the system through a refining tower. The copolymerization component in the first step is preferably the polycarboxylic acid, more preferably terephthalic acid.

The method for producing chemically recycled PET resin is not particularly limited as long as the above steps are met. For example, the direct esterification method is to directly react the chemically recycled BHET obtained by decomposing the polyester resin and other copolymer components as required, remove water and perform esterification, and then perform polycondensation under normal pressure or reduced pressure. Solid phase polymerization can also be performed as required to increase the inherent viscosity.

The first step can be carried out in one stage or in multiple stages. The polycondensation in the second step can be carried out in one stage or in multiple stages. In the case of multiple stages, a multi-tank method in which two or more polycondensation tanks are connected is preferred. In addition, the polycondensation in the second step can be carried out only by melt polymerization or by additionally polymerizing the chemically recycled PET resin produced by the melt polymerization method by solid phase polymerization.

(Polymerization Catalyst) The chemically recycled PET resin of the present invention is produced using a polymerization catalyst composed of an aluminum compound and a phosphorus compound. As a result, the chemically recycled PET resin of the present invention contains a catalytic amount of components derived from the aluminum compound and components derived from the phosphorus compound. In other words, the chemically recycled PET resin of the present invention contains aluminum atoms and phosphorus atoms.

As aluminum compounds and phosphorus compounds, the following can be listed.

(Aluminum compound) The aluminum compound is not limited as long as it is soluble in a solvent. Known aluminum compounds can be used without limitation. Among these, at least one selected from carboxylic acid salts, inorganic acid salts and chelates is preferred. Among these, at least one selected from aluminum acetate, alkaline aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxychloride and aluminum acetylacetonate is more preferred. At least one selected from aluminum acetate, alkaline aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride and aluminum acetylacetonate is more preferred. At least one selected from aluminum acetate and alkaline aluminum acetate is particularly preferred. Alkaline aluminum acetate is the most preferred.

It is preferred to use the aluminum compound as an aluminum compound solution dissolved in at least one solvent selected from the group consisting of water and alkanediols, because the effect of the present invention can be significantly exhibited. As the alkanediol, a solvent that dissolves the aluminum compound is preferably used, and more preferably, a diol such as ethylene glycol that is a constituent of the target polyester resin is used.

It is particularly preferred to use an alkanediol solution of an aluminum compound formed by adding an alkanediol to an aqueous solution of an aluminum compound and then diluting off the water. Specifically, the amount of alkanediol added is preferably 0.5 to 3 times the volume ratio of the aqueous solution of the aluminum compound. The solution after adding the alkanediol is preferably stirred at room temperature (e.g., 18 to 25°C) for several hours (e.g., 0.2 to 5 hours) to form a uniform water/alkanediol mixed solution. The solution is then heated to dilute off the water, thereby obtaining an alkanediol solution. The heating temperature is preferably 40 to 120°C. In addition, if necessary, the above heating can also be performed under reduced pressure (e.g., 1 to 30 kPa).

The concentration of the aluminum compound solution is preferably 10-30 g/L, more preferably 15-25 g/L.

The amount of aluminum compound added is preferably 5 to 70 mass ppm, more preferably 7 to 55 mass ppm, more preferably 8 to 50 mass ppm, more preferably 10 to 40 mass ppm, and particularly preferably 10 to 30 mass ppm, based on the content of aluminum atoms in chemically recovered PET. By adjusting the amount of aluminum atoms to 5 mass ppm or more, the polymerization activity can be further improved. On the other hand, by adjusting to 70 mass ppm or less, there is a tendency to further reduce the amount of aluminum-based foreign substances (especially foreign substances that are difficult to remove by filters). In particular, from the perspective of further reducing the amount of aluminum-based foreign substances, it is preferably 50 mass ppm or less. In addition, in this specification, mass ppm represents 10 ^-4 mass%.

Furthermore, if cost is important, the content of aluminum atoms in chemically recycled PET is preferably 9 to 20 mass ppm, more preferably 9 to 19 mass ppm, further preferably 10 to 17 mass ppm, and particularly preferably 12 to 17 mass ppm. By adjusting the amount of aluminum atoms to 9 mass ppm or more, the polycondensation rate can be further increased, and productivity can be ensured. On the other hand, by adjusting to 20 mass ppm or less, it is not related to the content of phosphorus atoms described later, and it is easy to suppress the increase in the amount of aluminum-based foreign matter (especially foreign matter that is difficult to remove by a filter), and the cost of the catalyst can be suppressed.

(Phosphorus compound) The phosphorus compound is not particularly limited. If a phosphonic acid compound and/or a phosphinic acid compound is used, the effect of improving the catalyst activity is increased and is preferred. Among these, if a phosphonic acid compound is used, the effect of improving the catalyst activity is particularly increased and is preferred.

Among the above-mentioned phosphorus compounds, phosphorus compounds having a phosphorus atom and a phenol structure in the same molecule are preferred. If the phosphorus compound having a phosphorus atom and a phenol structure in the same molecule is not particularly limited, if one or more compounds selected from the group consisting of phosphonic acid compounds having a phosphorus atom and a phenol structure in the same molecule and phosphinic acid compounds having a phosphorus atom and a phenol structure in the same molecule are used, the effect of improving the catalytic activity of the aluminum compound and the effect of improving the thermal stability of the resin are both increased and preferred, and if one or more phosphonic acid compounds having a phosphorus atom and a phenol structure in the same molecule are used, the effect of improving the catalytic activity and the effect of improving the thermal stability of the resin are both extremely large and preferred. The reason is believed to be that the phenol part (preferably a hindered phenol part) in the phosphorus compound improves the thermal stability of the chemically recycled PET resin.

In addition, examples of phosphorus compounds having a phosphorus atom and a phenol structure in the same molecule include compounds represented by P(=O)R ¹ (OR ² )(OR ³ ), P(=O)R ¹ R ⁴ (OR ² ), etc. R ¹ represents a phenol structure-containing alkyl group having 1 to 50 carbon atoms, a hydroxyl group, a halogen group, an alkoxy group, an amino group or other substituent, and a phenol structure-containing alkyl group having 1 to 50 carbon atoms. R ⁴ represents a hydrogen atom, a alkyl group having 6 to 50 carbon atoms, a alkyl group having 6 to 50 carbon atoms and a hydroxyl group, a halogen group, an alkoxy group, an amino group or other substituent. R ² and R ³ each independently represent a hydrogen atom, a alkyl group having 1 to 50 carbon atoms, a alkyl group having 1 to 50 carbon atoms and a hydroxyl group, an alkoxy group or other substituent. However, the alkyl group may not only be a straight chain structure, but may also contain a branched structure, an aliphatic ring structure such as cyclohexyl, or an aromatic ring structure such as phenyl or naphthyl. The ends of ^R2 and ^R3 , and ^R2 and ^R4 may also be bonded to each other.

Examples of the phosphorus compound having a phosphorus atom and a phenol structure in the same molecule include p-hydroxyphenylphosphonic acid, dimethyl p-hydroxyphenylphosphonate, diethyl p-hydroxyphenylphosphonate, diphenyl p-hydroxyphenylphosphonate, bis(p-hydroxyphenyl)phosphinic acid, methyl bis(p-hydroxyphenyl)phosphinic acid, phenyl bis(p-hydroxyphenyl)phosphinic acid, p-hydroxyphenylphosphinic acid, methyl p-hydroxyphenylphosphinic acid, and phenyl p-hydroxyphenylphosphinic acid.

As the phosphorus compound having a phosphorus atom and a phenol structure in the same molecule, in addition to the above examples, there can be cited: a phosphorus compound having a phosphorus atom and a hindered phenol structure (a phenol structure in which an alkyl group having a tertiary carbon (preferably an alkyl group having a tertiary carbon at the benzyl position such as t-butyl, tert-hexyl (thexyl) or neopentyl) is bonded to one or two adjacent positions of a hydroxyl group) in the same molecule, preferably a phosphorus compound having a phosphorus atom and the structure of the following (Formula A) in the same molecule, more preferably a compound represented by the following (Formula B), and even more preferably 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester in which ^X1 and ^X2 in the following (Formula B) are alkyl groups having 1 to 4 carbon atoms. In addition, the phosphorus compound used in the production of chemically recycled PET resin is preferably a compound represented by the following (Formula B) (preferably 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester), but in addition, it may also include a modified product of the compound represented by the following (Formula B) (preferably 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester). The details of the modified product are described in the following paragraph.

[Chemistry 1]

(In formula A, * represents a key).

[Chemistry 2]

(In (Formula B), X ¹ and X ² each represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms).

The chemically recycled PET of the present invention is preferably a polyester resin produced using a phosphorus compound having a phosphorus atom and a hindered phenol structure in the same molecule as a polymerization catalyst.

In the above (Formula B), X ¹ and X ² are both alkyl groups having 1 to 4 carbon atoms, more preferably alkyl groups having 1 to 2 carbon atoms. In particular, ethyl esters having 2 carbon atoms are preferred because they are commercially available as Irganox 1222 (manufactured by BASF) and are easily available.

The phosphorus compound is preferably heat-treated in a solvent for use. In addition, the details of the heat treatment are described in the latter section. When using 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester in the above (Formula B) as the phosphorus compound, a part of the 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester undergoes structural changes during the above heat treatment. For example, it may change due to the release of the tert-butyl group, the hydrolysis of the alkyl ester group (preferably the ethyl ester group), and the hydroxyethyl ester exchange structure (ester exchange structure with ethylene glycol). Therefore, in the present invention, as a phosphorus compound, in addition to 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester, a phosphorus compound with a changed structure may also be included. In addition, at the high temperature of the polymerization step, the tert-butyl group will obviously be separated.

The solvent used in the heat treatment is not limited as long as it is at least one selected from the group consisting of water and alkanediols. As alkanediols, it is preferable to use a solvent that dissolves the phosphorus compound, and it is more preferable to use a diol such as ethylene glycol as a component of the target polyester resin. The heat treatment in the solvent is preferably performed after the phosphorus compound is dissolved, but it is not necessarily completely dissolved. The temperature of the heat treatment is not particularly limited, and it is preferably 20~250℃, and more preferably 150~200℃. The time of the heat treatment is not particularly limited, and it is preferably 50~300 minutes, and more preferably 100~200 minutes. The concentration of the above-mentioned phosphorus compound solution is preferably 30~70g/L, and more preferably 40~60g/L.

The following shows nine phosphorus compounds in which a part of diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate undergoes structural changes when diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate is used as the phosphorus compound. The amount of each phosphorus compound undergoing structural changes in a diol solution can be quantified by P-NMR measurement.

[Chemistry 3]

Therefore, the phosphorus compound in the present invention may include, in addition to 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester, 9 modified forms of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid dialkyl ester as shown in the above chemical formula.

When the above-mentioned Irganox 1222 is used as the phosphorus compound, the chemically recycled PET resin preferably contains at least one of the nine phosphorus compound residues shown in Table 1 below. When at least one of the nine phosphorus compound residues shown in Table 1 is detected according to the P-NMR measurement method, it can be said that the chemically recycled PET resin is a chemically recycled PET resin produced using a phosphorus compound having a phosphorus atom and a hindered phenol structure in the same molecule as a polymerization catalyst. By using a phosphorus compound having a hindered phenol structure, the cost of the catalyst can be suppressed and sufficient polymerization activity can be exerted.

[Table 1]

In the present invention, it is preferred to include at least one of the above-mentioned formulas 1, 4 and 7.

The content of phosphorus atoms in chemically recycled PET is preferably 5-1000 mass ppm, more preferably 10-500 mass ppm, further preferably 15-200 mass ppm, particularly preferably 15-100 mass ppm, and most preferably 15-80 mass ppm. By adjusting the amount of phosphorus atoms to 5 mass ppm or more, the effect of increasing polymerization activity and the effect of suppressing the amount of aluminum-based foreign substances (especially foreign substances that are difficult to remove by filters) can be further improved. On the other hand, by adjusting it to less than 1000 mass ppm, the polymerization activity can also be increased, and the catalyst cost can be suppressed by reducing the amount of phosphorus compounds added.

In the case of paying more attention to cost, the content of phosphorus atoms in chemically recycled PET is preferably 13-31 mass ppm, more preferably 15-29 mass ppm, and even more preferably 16-28 mass ppm. By adjusting the amount of phosphorus atoms to 13 mass ppm or more, the effect of increasing polymerization activity and the effect of suppressing the amount of aluminum-based foreign substances (especially foreign substances that are difficult to remove by filters) can be further improved. On the other hand, by adjusting it to 31 mass ppm or less, the polymerization activity can be further increased, and by further reducing the amount of phosphorus compounds added, the catalyst cost can be further suppressed.

In chemically recycled PET, the molar ratio of phosphorus atoms to aluminum atoms is preferably 1.00-5.00, more preferably 1.10-4.00, further preferably 1.20-3.50, and particularly preferably 1.25-3.00. As described above, the aluminum atoms and phosphorus atoms in chemically recycled PET are derived from the aluminum compound and phosphorus compound used as polymerization catalysts, respectively. By using these aluminum compounds and phosphorus compounds in a specific ratio, a complex having a catalytic activity in the polymerization system is formed, and sufficient polymerization activity can be exerted. In addition, the resin produced using a polymerization catalyst composed of an aluminum compound and a phosphorus compound has a higher catalyst cost (high manufacturing cost) compared to a chemically recycled PET resin produced using an antimony catalyst, but by using an aluminum compound and a phosphorus compound in a specific ratio, the catalyst cost can be suppressed and sufficient polymerization activity can be exerted. By adjusting the residual molar ratio of phosphorus atoms to aluminum atoms to 1.00 or more, the thermal stability and thermal oxidation stability can be improved, and the amount of aluminum-based foreign matter (especially foreign matter that is difficult to remove by a filter) can be further suppressed. On the other hand, by adjusting the residual molar ratio of phosphorus atoms to aluminum atoms to 5.00 or less, the amount of phosphorus compounds added can be reduced, thereby suppressing the catalyst cost. When cost is more important, the residual molar ratio of phosphorus atoms to aluminum atoms should be 1.32~1.80, and more preferably 1.38~1.68.

As described above, by adjusting the content of aluminum atoms and phosphorus atoms, and the molar ratio of phosphorus atoms to aluminum atoms, the amount of foreign matter that is difficult to remove by the filter can be further suppressed. Foreign matter functions as a crystallizing agent, which accelerates the crystallization rate of chemically recycled PET resin. Therefore, when there are a lot of foreign matter in chemically recycled PET resin, the resin is easy to crystallize during processing, and there is also a concern that the resin whitens, resulting in reduced transparency and other quality deterioration. In addition, in order to improve transparency, there is also a method of adding copolymer components such as isophthalic acid to polyethylene terephthalate resin to reduce the crystallization rate, but this method is suspected of causing a decrease in the physical properties of the resin. On the other hand, the chemically recycled PET resin of the present invention has a suppressed amount of foreign matter and a suppressed crystallization rate, so it does not contain copolymer components such as isophthalic acid or contains a small amount of such components, which is also preferable.

(Catalysts other than aluminum compounds and phosphorus compounds) In addition, in the present invention, in addition to the above-mentioned aluminum compounds and phosphorus compounds, other polymer catalysts such as antimony compounds, germanium compounds, titanium compounds, and cobalt compounds may also be used in combination as long as the properties, processability, color tone, etc. of the chemically recycled PET resin of the present invention do not cause problems in the product.

The content of antimony atoms in the chemically recycled PET resin of the present invention is preferably 100 mass ppm or less, more preferably 50 mass ppm or less, and further preferably 20 mass ppm or less. The content of germanium atoms in the chemically recycled PET resin of the present invention is preferably 40 mass ppm or less, and more preferably 20 mass ppm or less. The content of titanium atoms in the chemically recycled PET resin of the present invention is preferably 10 mass ppm or less, and more preferably 5 mass ppm or less. The content of cobalt atoms in the chemically recycled PET resin of the present invention is preferably 40 mass ppm or less, and more preferably 20 mass ppm or less.

However, considering the purpose of the present invention, it is preferred not to use the above-mentioned other polymerization catalysts as much as possible.

By using aluminum compounds and phosphorus compounds as polymerization catalysts, the amount of foreign matter is reduced compared to the case of using other polymerization catalysts (such as titanium compounds, antimony compounds, etc.), but in order to further reduce the amount of foreign matter, it is preferable to add the polymerization catalyst from the end of the first step to the start of the second step. The so-called "before the start of the second step" mentioned above includes the time point when the pressure is reduced and the polycondensation is started. In addition, as mentioned above, when adding aluminum compounds and phosphorus compounds, it is preferable to add them as aluminum compound solutions and phosphorus compound solutions.

In addition, the amount of free ethylene glycol components in chemically recovered BHET is uneven in each batch, so the amount of free ethylene glycol in chemically recovered BHET should not only be kept below a certain amount, but also the amount of free ethylene glycol components contained in the reaction solution at the end of the first step when chemically recovered PET resin is produced using chemically recovered BHET should be reduced as much as possible. The amount of free ethylene glycol components is preferably 1.5 mol% or less relative to 100 mol% of the total amount of all polyol components contained in the reaction solution at the end of the first step. It is more preferably 1.0 mol% or less, more preferably 0.7 mol% or less, and particularly preferably 0.5 mol% or less.

In order to minimize the amount of free ethylene glycol contained in the reaction solution at the end of the first step, for example, the first step is preferably performed in a short time.

The reaction temperature is preferably 80~285℃, more preferably 90~282℃, more preferably 100~280℃, and particularly preferably 110~278℃. The pressure is preferably 0.05~0.60MPa, more preferably 0.055~0.55MPa, more preferably 0.060~0.50MPa, and particularly preferably 0.065~0.45MPa. The reaction time is preferably less than 200 minutes, more preferably less than 195 minutes, more preferably less than 190 minutes, and particularly preferably less than 185 minutes. By using a raw material containing chemically recovered BHET, the esterification reaction can be performed without esterification reaction or in a short time, in which case the generation of free ethylene glycol can be suppressed. In addition, when only chemically recovered BHET is used as a raw material, the first step is sometimes terminated when the chemically recovered BHET is added to the reaction vessel and melted.

Furthermore, it is also preferable to add an alkali during the first step (e.g., during the esterification reaction). In this case, the first step can be performed in a short time. Examples of the alkali include tertiary amines such as triethylamine, tri-n-butylamine, and benzyldimethylamine, quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, and trimethylbenzylammonium hydroxide, and lithium carbonate, sodium carbonate, potassium carbonate, and sodium acetate.

The amount of alkali added is preferably 0.01 mol%, more preferably 0.05 mol%, and even more preferably 0.1 mol% relative to 100 mol% of all polycarboxylic acid components in the chemically recovered BHET. The upper limit of the amount of alkali is preferably 2 mol%, more preferably 1.5 mol%, and even more preferably 1 mol%.

In the production of the chemically recycled PET resin of the present invention, the acid value of the reaction intermediate oligomer after the first step (such as esterification reaction) is preferably 80~2000eq/ton, and the hydroxyl value is preferably 2800~8000eq/ton. In this way, the reaction rate of the polycondensation reaction can be increased. As for the physical properties of the reaction intermediate oligomer, the acid value is more preferably 90~1900eq/ton, and the hydroxyl value is more preferably 3000~7800eq/ton. The oligomer in the present invention refers to the reaction intermediate after the first step (such as esterification reaction) is completed and before the polycondensation reaction is carried out. If there are unreacted raw materials, it means that the reaction intermediates of such unreacted raw materials are also included.

In order to reduce the amount of foreign matter in the chemically recycled PET resin, for example, it is also preferable to perform the second step in a short time.

Therefore, it is preferable to carry out the first step in the presence of terephthalic acid. That is, it is preferable to add terephthalic acid to chemically recover BHET and carry out the first step in the presence of terephthalic acid. In this case, the reaction is activated due to the acid group of terephthalic acid, and the second step can be carried out in a short time, which can reduce the thermal history in the polycondensation reaction. When an acid component is added, it is preferable to carry out the esterification reaction of the acid component in a short time. Specifically, for example, the first step is carried out while removing the water or alcohol generated by the reaction to the outside of the system by a distillation tower. The temperature of the first step is preferably 80~285°C, more preferably 90~282°C, more preferably 100~280°C, and particularly preferably 110~278°C. It is preferably carried out under a pressure of 0.05-0.60MPa, more preferably 0.055-0.55MPa, more preferably 0.060-0.50MPa, and particularly preferably 0.065-0.45MPa. The reaction time is preferably less than 200 minutes, more preferably within 195 minutes, more preferably within 190 minutes, particularly preferably within 185 minutes, and most preferably within 100 minutes. The amount of added terephthalic acid (hereinafter sometimes referred to as added terephthalic acid) is preferably less than 40 mol% relative to the total of 100 mol% of all polycarboxylic acid components and added terephthalic acid in the chemically recovered BHET. It is more preferably less than 30 mol% and even more preferably less than 20 mol%.

In order to carry out the second step in a short time, it is advisable to adjust the temperature and reduce the pressure while carrying out polycondensation to increase the degree of polymerization in a short time. In the initial stage of polycondensation, the temperature is preferably 260~270℃ and the pressure is preferably 0.01~0.001MPa. While slowly raising the temperature, the pressure is reduced, and finally the optimal temperature is 270~285℃ and the optimal pressure is 0.0002~0.000005MPa or 0.00002~0.000005MPa. The time of the polycondensation reaction, from the time the above temperature is reached to the end, is preferably within 200 minutes, more preferably within 180 minutes, more preferably within 160 minutes, particularly preferably within 140 minutes, and most preferably within 120 minutes. Also, starting from the addition of the reactants after the completion of the first step, the temperature should be quickly raised to the initial temperature. In order to shorten the heating time, the size and shape of the reaction vessel should be optimized by increasing the surface area relative to the contents, and the amount of reactants added after the completion of the first step should be optimized. Also, sufficient stirring should be performed. It is important to optimize the amount of polycondensation catalyst added to obtain a high polymerization rate and to perform sufficient stirring to renew the catalyst surface. If the amount of catalyst is too much, it may become a foreign matter and cause the transparency of the film to decrease or defects to increase. Depending on the purpose of the film, the amount of catalyst should be increased within a range that allows for these problems. Considering the appropriate amount of catalyst and stirring, the polycondensation reaction time should be more than 30 minutes, and more preferably more than 45 minutes.

Among the raw materials of chemically recycled PET, the chemically recycled BHET is preferably 50 mass % or more, more preferably 60 mass % or more, further preferably 70 mass % or more, particularly preferably 80 mass % or more, most preferably 90 mass % or more, and 100 mass % is also preferred.

In the chemically recycled PET resin thus obtained, the amount of foreign matter with a particle size of 0.50-0.69 μm obtained by a particle counter is less than 2000 pieces/ml, preferably less than 1500 pieces/ml, more preferably less than 800 pieces/ml, particularly preferably less than 300 pieces/ml, and most preferably less than 150 pieces/ml. By adjusting the amount of foreign matter to the above range, the reduction in transparency and the deterioration in the quality of the molded product can be suppressed.

The lower limit of the cooling and crystallization temperature of the chemically recycled PET resin is, for example, 175°C or higher, preferably 178°C or higher, more preferably 180°C or higher, particularly preferably 183°C or higher, and most preferably 185°C or higher. The upper limit of the cooling and crystallization temperature of the chemically recycled PET resin is, for example, 202°C or lower, preferably 200°C or lower, more preferably 198°C or lower, particularly preferably 196°C or lower, and most preferably 194°C or lower. That is, the cooling and crystallization temperature of the chemically recycled PET resin is, for example, 175-202°C, preferably 178-200°C, more preferably 180-198°C, further preferably 183-196°C, and particularly preferably 185-194°C.

Relative to 100 mol% of all polycarboxylic acid components in chemically recycled PET resin, the lower limit of the terephthalic acid component is preferably 98 mol%, then 98.3 mol%, more preferably 98.5 mol%, more preferably 98.8 mol%, particularly preferably 99 mol%, and most preferably 99.2 mol%. The upper limit of the terephthalic acid component is preferably 99.98 mol%, more preferably 99.95 mol%, and can also be 99.9 mol%, 99.85 mol% or 99.8 mol%. In addition, in this specification, the so-called lower limit of 98 mol% means 98 mol% or more, and can also exceed 98 mol%. In addition, in this specification, the so-called upper limit of 99.98 mol% means 99.98 mol% or less, and can also be less than 99.98 mol%. The same applies to the upper and lower limits of other components and physical properties. That is, relative to 100 mol% of all polycarboxylic acid components in the chemically recycled PET resin, the amount of terephthalic acid component is preferably 98-99.98 mol%, more preferably 98.3-99.95 mol%, and can also be 98.5-99.9 mol%, 98.8-99.85 mol%, 99-99.8 mol% or 99.2-99.8 mol%.

Relative to 100 mol% of all polycarboxylic acid components in chemically recycled PET resin, the lower limit of the amount of isophthalic acid component is preferably 0.02 mol%, more preferably 0.05 mol%, and can also be 0.1 mol%, 0.15 mol% or 0.2 mol%. In this case, the crystallization rate can be optimized to obtain a resin with high transparency. The upper limit of the amount of isophthalic acid component is preferably 2 mol%, then 1.7 mol%, more preferably 1.5 mol, more preferably 1.2 mol, particularly preferably 1 mol, and most preferably 0.8 mol%, and can also be 0.15 mol%. In addition, the so-called upper limit of 2 mol% means less than 2 mol%, and can also be less than 2 mol%. That is, the amount of isophthalic acid component relative to 100 mol% of all polycarboxylic acid components in the chemically recycled PET resin is preferably 0.02-2 mol%, more preferably 0.05-1.7 mol%, and can also be 0.1-1.5 mol%, 0.15-1.2 mol%, 0.2-1 mol% or 0.02-0.15 mol%.

Relative to 100 mol% of all polyol components in the chemically recycled PET resin, the lower limit of the amount of ethylene glycol components is preferably 97.5 mol%, more preferably 97.7 mol%, more preferably 97.8 mol%, particularly preferably 97.9 mol%, and best 98 mol%. The upper limit of the amount of ethylene glycol components is preferably 99.3 mol%, more preferably 99.1 mol%, more preferably 99 mol, particularly preferably 98.9 mol, and best 98.8 mol%. That is, relative to 100 mol% of all polyol components in the chemically recycled PET resin, the amount of ethylene glycol components is preferably 97.5~99.3 mol%, more preferably 97.7~99.1 mol%, more preferably 97.8~99 mol%, particularly preferably 97.9~98.9 mol, and best 98~98.8 mol%.

Relative to 100 mol% of all polyol components in the chemically recycled PET resin, the lower limit of the amount of diethylene glycol is preferably 0.7 mol%, more preferably 0.9 mol%, more preferably 1 mol, particularly preferably 1.1 mol, and the best is 1.2 mol. The upper limit of the amount of diethylene glycol is preferably 2.5 mol, more preferably 2.3 mol, more preferably 2.1 mol, particularly preferably 1.9 mol, and the best is 1.7 mol. That is, relative to 100 mol% of all polyol components in the chemically recycled PET resin, the amount of diethylene glycol is preferably 0.7~2.5 mol, more preferably 0.9~2.3 mol, more preferably 1~2.1 mol, particularly preferably 1.1~1.9 mol, and the best is 1.2~1.7 mol. By adjusting the diethylene glycol content to the above range, the chemically recycled PET resin can have a high degree of thermal stability and can suppress the coloring of the resin. In particular, if the diethylene glycol content exceeds 2.5 mol%, the inherent viscosity retention rate of the chemically recycled PET resin may decrease and the mechanical properties of the molded product may decrease.

When the amount of terephthalic acid component relative to 100 mol% of all polycarboxylic acid components in the chemically recycled PET resin is set as TPA(r) mol%, and the amount of ethylene glycol component relative to 100 mol% of all polyol components in the chemically recycled PET resin is set as EG(r) mol%, the lower limit of the value of 200-TPA(r)-EG(r) is preferably 0.8 mol%, more preferably 0.9 mol, further preferably 1 mol, and particularly preferably 1.2 mol. The upper limit of the value of 200-TPA(r)-EG(r) is preferably 4 mol, more preferably 3.5 mol, further preferably 3.2 mol, particularly preferably 3.0 mol, and most preferably 2.8 mol. That is, the value of 200-TPA(r)-EG(r) is preferably 0.8~4 mol%, more preferably 0.9~3.5 mol%, still more preferably 1~3.2 mol%, particularly preferably 1.2~3.0 mol%, and most preferably 1.2~2.8 mol%.

By making the composition of the chemically recycled PET resin within the above range, coloration can be suppressed and a high degree of thermal stability can be achieved.

(Physical properties of chemically recycled PET resin) For chemically recycled PET resin, the lower limit of the intrinsic viscosity is preferably 0.5dL/g, more preferably 0.55dL/g, and more preferably 0.58dL/g. The upper limit of the intrinsic viscosity is preferably 0.8dL/g, more preferably 0.77dL/g, and more preferably 0.75dL/g. That is, the intrinsic viscosity of chemically recycled PET resin is preferably 0.5~0.8dL/g, more preferably 0.55~0.77dL/g, and more preferably 0.58~0.75dL/g. By making it within the above range, the strength and film-making stability of the film can be ensured. In order to obtain chemically recycled PET with high intrinsic viscosity, solid phase polymerization is preferably performed after melt polymerization.

The lower limit of the acid value of chemically recycled PET resin is preferably 0 equivalents/ton, more preferably 1 equivalents/ton, more preferably 2 equivalents/ton, particularly preferably 3 equivalents/ton, and the best is 4 equivalents/ton. In order to reduce the acid value, solid phase polymerization is preferably performed. In the case of no solid phase polymerization, the lower limit of the acid value of PET is preferably 15 equivalents/ton, more preferably 20 equivalents/ton, more preferably 23 equivalents/ton, and particularly preferably 25 equivalents/ton. The upper limit is preferably 60 equivalents/ton, more preferably 55 equivalents/ton, more preferably 50 equivalents/ton, particularly preferably 45 equivalents/ton, and the best is 40 equivalents/ton. That is, the acid value of chemically recycled PET resin is preferably 0-60 equivalents/ton, more preferably 1-55 equivalents/ton, more preferably 2-50 equivalents/ton, particularly preferably 3-45 equivalents/ton, and most preferably 4-40 equivalents/ton. It can also be 15-60 equivalents/ton, 20-60 equivalents/ton, 23-60 equivalents/ton, or 25-60 equivalents/ton. By keeping it within the above range, the productivity of chemically recycled PET can be ensured, and the acid value of the obtained film can be within the appropriate range. In order to keep the acid value within the above range, it is advisable to adopt methods such as maintaining the above appropriate temperature during polycondensation, reducing the pressure, and replacing the reaction container with inactive gases such as nitrogen to form a low oxygen state during polycondensation.

The inherent viscosity retention rate of chemically recycled PET after melt kneading is preferably 89% or more, more preferably 90% or more, further preferably 91% or more, and particularly preferably 92% or more. If the inherent viscosity retention rate is lower than 89%, there is a concern that the thermal stability of the resin is low and the mechanical properties of the molded product are insufficient. In addition, in this manual, when simply recorded as "inherent viscosity retention rate", it refers to the inherent viscosity retention rate after kneading after one melt kneading.

The color b value of chemically recycled PET resin is preferably 10 or less, more preferably 8 or less, still more preferably 5 or less, and particularly preferably 3 or less. The color b value is a yellow/blue coordinate, with positive values indicating yellow and negative values indicating blue. It is believed that the color b value is affected by the amount of foreign matter and thermal stability of the chemically recycled PET resin.

This application claims the benefit of priority based on Japanese Patent Application No. 2022-130235 filed on August 17, 2022 and Japanese Patent Application No. 2023-005108 filed on January 17, 2023. All contents of the specification of Japanese Patent Application No. 2022-130235 filed on August 17, 2022 and all contents of the specification of Japanese Patent Application No. 2023-005108 filed on January 17, 2023 are incorporated herein by reference. [Example]

Hereinafter, the present invention will be described by way of embodiments, but the present invention is of course not limited to these embodiments.

(1) Intrinsic viscosity (IV) About 3 g of PET resin was frozen and crushed, dried at 140°C for 15 minutes, and 0.20 g was weighed. 20 ml of a mixed solvent of 1,1,2,2-tetrachloroethane and p-chlorophenol in a mass ratio of 1:3 was stirred at 100°C for 60 minutes to completely dissolve the mixture. After cooling to room temperature, the mixture was passed through a glass filter to prepare a sample. Using an Ubeloch viscometer (manufactured by Chemtech Co., Ltd.) adjusted to 30°C, the falling time of the sample and the solvent was measured, and the intrinsic viscosity [η] was calculated using the following formula. [η]=(-1+√(1+4K'η _sp ))/2K'C η _sp =(τ-τ ₀ )/τ ₀ Here, [η]: intrinsic viscosity (dl/g) η _sp : specific viscosity (-) K': Huggins constant (=0.33) C: concentration (=1g/dl) τ: sample falling time (sec) τ ₀ : solvent falling time (sec)

(2) Content of a given metal atom in the sample Weigh the PET resin and place it in a platinum crucible. Carbonize it in an electric furnace and then ash it in a muffle furnace at 550°C for 8 hours. The ash-treated sample is dissolved in 1.2M hydrochloric acid to prepare a sample solution. The prepared sample solution is measured under the following conditions to determine the concentrations of antimony atoms, aluminum atoms, titanium atoms, germanium atoms, and cobalt atoms in the PET resin by high-frequency inductively coupled plasma emission spectrometry. Equipment: CIROS-120 manufactured by SPECTRO Plasma output: 1400W Plasma gas: 13.0L/min Auxiliary gas: 2.0L/min Atomizer: Staggered atomizer Chamber: Cyclone chamber Measurement wavelength: 167.078nm

(3) Phosphorus atom content in PET resin PET resin was wet-decomposed with sulfuric acid, nitric acid, and perchloric acid, and then neutralized with ammonia water. After adding ammonium molybdate and hydrazine sulfate to the prepared solution, the absorbance at a wavelength of 830nm was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-1700). The concentration of phosphorus atoms in PET resin was calculated from the calibration curve prepared in advance.

(4) Contents of polycarboxylic acid components and polyol components, polymer acid value, oligomer acid value, and oligomer hydroxyl value in PET resin ･The amount of polycarboxylic acid components in PET resin is calculated as the amount of each polycarboxylic acid component relative to 100 mol% of all polycarboxylic acid components (mol%). ･The amount of polyol components in PET resin is calculated as the amount of each polyol component relative to 100 mol% of all polyol components (mol%). ･Polymer acid value (AV) is calculated as the equivalent of acid per ton of PET resin (unit: eq/ton). ･Oligomer acid value (OLG-AV) is calculated as the equivalent of acid per ton of oligomer (unit: eq/ton). ･Oligomer hydroxyl value (OLG-OHV) is calculated as the equivalent of hydroxyl groups per ton of oligomer (unit: eq/ton). (Measurement method) Dissolve 20 mg of PET resin in 0.6 ml of a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform at a ratio of 1:9 (volume ratio) and centrifuge. Collect the supernatant and perform H-NMR measurement under the following conditions. Apparatus: Fourier transform nuclear magnetic resonance apparatus (made by BRUKER, AVANCE NEO600) ¹ H resonance frequency: 600.13 MHz Locking solvent: deuterated chloroform Deflection angle: 30° Data reception time: 4 seconds Delay time: 1 second Measurement temperature: 30°C Accumulated times: 128 times

(5) Calculation of the hydroxyl ratio of oligomers (OLG-OH%) The hydroxyl ratio is calculated from the acid value and hydroxyl value obtained by the above method using the following formula. The end of the oligomer is taken as the sum of the acid value and the hydroxyl value. Hydroxy ratio = {hydroxyl value/(hydroxyl value + acid value)} × 100

(6) Contents of polycarboxylic acid components and polyol components in chemically recovered BHET Chemically recovered BHET was dissolved in deuterated methanol and H-NMR measurement was performed under the following conditions. Apparatus: Fourier transform nuclear magnetic resonance apparatus (manufactured by BRUKER) ¹ H resonance frequency: 500.13 MHz Locking solvent: deuterated methanol Deflection angle: 45° Data reception time: 4 seconds Delay time: 1 second Measurement temperature: 27°C Accumulated times: 36 times

(7) Foreign matter 0.06 g of PET resin was dissolved in 100 ml of HFIP (hexafluoro-2-propanol) and measured using a particle counter to evaluate the number of particles with a particle size of 0.50 to 0.69 μm. AccuSizer A7000/SIS, manufactured by Japan Intertec Co., Ltd. Measuring range: 0.5 to 400 μm

(8) Cooling crystallization temperature (Tc2) Using the differential scanning calorimeter "DSC220" manufactured by SEICO Electronics Industrial Co., Ltd., 5 mg of PET resin was placed in an aluminum pot, covered with a lid and sealed. Then, it was kept at 290°C for 5 minutes and then cooled at a cooling rate of 10°C/min. The peak value of the heat peak obtained during cooling was taken as the cooling crystallization temperature.

(9) Color b value of PET resin Put about 50g of PET resin into the measurement container and measure it while rotating it. The color b value is measured from the three stimulus values XYZ that represent the basic color stimulus. The higher the value, the stronger the yellow tone. Equipment: Tokyo Denshoku Co., Ltd. Precision Spectrophotometer TC-1500SX Measurement method: According to JIS Z8722 Transmitted light 0 degree, -0 degree method Detection element: Silicon photodiode array Light source: Halogen lamp 12V100W 2000H Measurement area: Transmitted 25mmφ Humidity and temperature conditions: 25℃, RH50% Measurement container: φ35mm, height 25mm Rotary type (particles) Measurement content: X, Y, Z three stimulus values CIE chromaticity coordinates x=X/(X+Y+Z) y=Y/(X+Y+Z)

(10) Thermal decomposition test The PET resin was vacuum dried at 140°C for 16 hours to produce a dried crystallized polyester with a moisture content of less than 150 ppm. The dried crystallized polyester was used to measure the inherent viscosity (IV after treatment) after melt kneading in a biaxial extruder under the following conditions, and the inherent viscosity retention rate (IV retention rate) was calculated using the following formula. Double-screw extruder: KZW15TW-45/60MG-NH (-2200) manufactured by TECHNOVEL Set temperature: 300°C Screw rotation speed: 200rpm Discharge rate: 1.7~2.0kg/h Intrinsic viscosity retention rate (%) = 100×Intrinsic viscosity after kneading/Intrinsic viscosity before kneading In addition, the moisture content was measured using a Karl Fischer moisture meter (CA-200 manufactured by Mitsubishi Chemical Analytech Co., Ltd.) using the electrometric titration method at 230°C, 5 minutes, and 250mL/min nitrogen flow for 0.6g of the sample.

The following describes the preparation of aluminum-containing ethylene glycol solution, phosphorus-containing ethylene glycol solution and chemically recovered BHET.

(Preparation of ethylene glycol solution containing aluminum) For a 20g/L aqueous solution of alkaline aluminum acetate, an equal amount (volume ratio) of ethylene glycol is placed in a mixing tank, stirred at room temperature (23°C) for several hours, and then stirred at 50-90°C for several hours under reduced pressure (3kPa) while distilling water from the system to prepare an ethylene glycol solution containing aluminum compounds containing 20g/L.

(Preparation of phosphorus-containing ethylene glycol solution t) Irganox 1222 (manufactured by BASF) was placed in a mixing tank together with ethylene glycol as a phosphorus compound, and heat-treated at 175°C for 150 minutes while stirring under nitrogen substitution to prepare a phosphorus-containing ethylene glycol solution t containing 50 g/L of a phosphorus compound.

(Preparation of chemically recovered BHET) The following (j) to (l) were mixed so that the chemically recovered BHET had a composition ratio as shown in Table 2, thereby preparing CR-BHET1, CR-BHET2, and CR-BHET3. (j) Chemically recovered BHET containing isophthalic acid components obtained from recycled beverage bottles (k) Chemically recovered BHET containing diethylene glycol components obtained from recycled beverage bottles (l) Chemically recovered BHET containing isophthalic acid components obtained from recycled PET films

[Table 2] CR-BHET1 CR-BHET2 CR-BHET3 TPA content in CR-BHET (mol % relative to polycarboxylic acid component) 99.95 99.95 99.95 IPA content in CR-BHET (mol %, relative to all polycarboxylic acid components) 0.05 0.05 0.05 EG content in CR-BHET (mol %, relative to all polyol components) 99.0 98.8 98.8 DEG content in CR-BHET (mol %, relative to all polyol components) 1.0 1.2 1.2 Amount of free EG in CR-BHET (mol%, relative to all polyol components) 0.1 0.6 2.4 Amount of all polyol components in CR-BHET (mol % relative to all polycarboxylic acid components) 210 210 210 (100-TPA(b))+(100-EG(b))*2 2.1 2.5 2.5

In addition, TPA refers to terephthalic acid, IPA refers to isophthalic acid, EG refers to ethylene glycol, and DEG refers to diethylene glycol. TPA(b) and EG(b) are as described above.

Example 1 In a 5L stainless steel autoclave with a stirrer, CR-BHET1 in Table 2 was added as chemically recovered BHET, and triethylamine was added as an alkali in an amount of 0.3 mol% relative to the terephthalic acid component in the chemically recovered BHET. Then, BHET was melted to obtain an oligomer (Step 1). The characteristics of the oligomer after Step 1 were that OLG-AV was 100 eq/t, OLG-OHV was 7600 eq/t, and when the total amount of all polyol components contained in the reaction solution was set to 100 mol%, the free ethylene glycol content was 0.1 mol%. Then, a mixed solution prepared by mixing the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t prepared by the above method and converting them into a single liquid was added. In addition, the mixed liquid is added in such a way that the amount of aluminum atoms and phosphorus atoms in the chemically recycled PET becomes 30 mass ppm and 74 mass ppm. The molar ratio of phosphorus atoms to aluminum atoms is (P/Al) = 2.15. Afterwards, the system temperature is raised to 278°C while stirring. During this period, the system pressure is slowly reduced to 0.1kPa. Under this condition, a polycondensation reaction is carried out, and then the obtained molten resin is supplied to a strand cutter to obtain a granular chemically recycled PET resin. The time from the start of temperature rise to the end of the reaction is 180 minutes.

Example 2 Other than using CR-BHET2 listed in Table 2 as chemically recovered BHET, the same operation as in Example 1 was performed.

Examples 3 to 5 CR-BHET1 and terephthalic acid (hereinafter sometimes referred to as added terephthalic acid) were added together. The molar ratio of CR-BHET1 and added terephthalic acid, the time of the first step, and the condensation time were set to the conditions in Table 3. Other than that, the operation was performed in the same manner as in Example 1.

Example 6 Other than using the chemically recycled PET resin in an amount of 15 ppm by mass of aluminum atoms and 38 ppm by mass of phosphorus atoms, the same operation as in Example 4 was performed. The molar ratio of phosphorus atoms to aluminum atoms (P/Al) = 2.20.

Examples 7 and 8 CR-BHET1 and CR-BHET3 were added in a molar ratio as shown in Table 3, and the same operation as in Example 1 was performed.

Comparative Example 1 Other than using CR-BHET3 in Table 2 as chemically recovered BHET, the same operation as in Example 1 was performed.

Comparative Example 2 An antimony catalyst was added in a manner such that the antimony atoms contained in the chemically recovered PET resin became 200 mass ppm instead of adding the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t, and the condensation time was changed to the time recorded in Table 3. The operation was carried out in the same manner as in Example 1.

Comparative Example 3 The same operation as in Example 1 was performed except that a titanium catalyst was added in such a manner that the titanium atom contained in the chemically recovered PET resin became 30 mass ppm instead of the addition of the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t, and the polycondensation time was changed to the time shown in Table 3.

Comparative Example 4 At the same time as adding CR-BHET1, tributyl phosphate was added in such a way that the phosphorus atoms contained in the chemically recovered PET resin became 30 ppm, instead of adding the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t, and 2.5 g/L of germanium dioxide-containing ethylene glycol solution was added in such a way that the germanium atoms contained in the chemically recovered PET resin became 115 mass ppm, and the condensation time was set to the conditions in Table 3. Other than that, the operation was carried out in the same manner as in Example 1.

Comparative Example 5 At the same time as adding CR-BHET1, tributyl phosphate was added in such a way that the phosphorus atoms contained in the chemically recovered PET resin became 30 ppm, instead of adding the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t, 4.5 g/L of ethylene glycol solution containing antimony trioxide was added in such a way that the antimony atoms contained in the chemically recovered PET resin became 700 mass ppm, and the condensation time was set to the conditions in Table 3. Other than that, the operation was carried out in the same manner as in Example 1.

Comparative Example 6 2.5 g/L of ethylene glycol solution containing antimony trioxide, 2.5 g/L of ethylene glycol solution containing cobalt acetate, 2.5 g/L of ethylene glycol solution containing phosphoric acid, and titanium oxide (product name SA-1: manufactured by Sakai Chemical Industry) were added instead of adding aluminum-containing ethylene glycol solution s and phosphorus-containing ethylene glycol solution t, and the condensation time was set to the conditions in Table 3. The same operation as in Example 1 was performed except that. In addition, 2.5 g/L of ethylene glycol solution containing antimony trioxide was added in such a way that the antimony atoms contained in the chemically recovered PET resin became 250 mass ppm, 2.5 g/L of ethylene glycol solution containing cobalt acetate was added in such a way that the cobalt atoms contained in the chemically recovered PET resin became 57 mass ppm, 2.5 g/L of ethylene glycol solution containing phosphoric acid was added in such a way that the phosphorus atoms contained in the chemically recovered PET resin became 17 mass ppm, and titanium oxide was added in such a way that it became 3000 mass ppm relative to the chemically recovered PET resin.

Comparative Example 7 At the same time as adding CR-BHET1, an 85 wt% phosphoric acid aqueous solution was added in such a way that the phosphorus atoms contained in the chemically recovered PET resin became 20 ppm, instead of adding the aluminum-containing ethylene glycol solution s and the phosphorus-containing ethylene glycol solution t, and germanium dioxide was added in such a way that the germanium atoms contained in the chemically recovered PET resin became 100 mass ppm, and the condensation time was set to the conditions in Table 3. Other than that, the operation was performed in the same manner as in Example 1.

Reference Example 1 In a 5L stainless steel autoclave with a stirrer, high-purity terephthalic acid and 2.0 times the molar amount of ethylene glycol were placed, and 0.4 mol% of triethylamine relative to the polycarboxylic acid component was added. Under a pressure of 0.25 MPa, an esterification reaction was carried out at 245°C while distilling water out of the system to obtain a mixture of BHET and oligomers. Thereafter, the same operation as in Example 1 was performed.

Reference Example 2 Other than adding 1.3 times the molar amount of ethylene glycol relative to high purity terephthalic acid, the same operation as in Reference Example 1 was performed.

The results are shown in Table 3. Example 2 is an example in which the amount of free ethylene glycol is increased compared to Example 1. Although a slight difference in the amount of foreign matter is confirmed, there is no problem. Comparative Example 1 is an example in which the amount of free ethylene glycol is greatly increased, and the amount of foreign matter is significantly increased. In addition, Examples 7 and 8 are examples in which the usage ratio of CR-BHET1 and CR-BHET3 is changed. By blending CR-BHET1 and CR-BHET3 together, the amount of free ethylene glycol in CR-BHET is increased (the amount of free ethylene glycol component in 100 mol% of all polyol components of CR-BHET: 1.0 mol% in Example 7 and 1.3 mol% in Example 8). Although a slight increase in the amount of foreign matter is confirmed, there is no problem. Examples 3 to 5 are examples of changing the ratio of CR-BHET and added terephthalic acid. Although a slight difference was confirmed in the amount of foreign matter, there was no problem. Example 6 is an example of changing the amount of Al catalyst and Ti catalyst. Although a slight difference was confirmed in the amount of foreign matter, there was no problem. Comparative Examples 2, 3, 4, and 7 are examples of changing the metal type and/or phosphorus compound of the catalyst. The amount of foreign matter increased significantly. Comparative Example 5 is an example of using an ethylene glycol solution of antimony trioxide as an antimony catalyst and tributyl phosphate as a phosphorus compound. The amount of foreign matter increased significantly. This is believed to be because the use of a dilute antimony-based ethylene glycol solution further increases the amount of free ethylene glycol after adding the catalyst compared to Comparative Example 2, and the absolute amount of the catalyst is also large, which leads to an increase in the amount of foreign matter. Comparative Example 6 is an example in which a cobalt compound and titanium oxide are added to suppress the color b value, and the amount of foreign matter increases significantly. In addition, the amount of free ethylene glycol in the oligomers made from terephthalic acid and ethylene glycol in Reference Examples 1 and 2 is greater than that in the oligomer using CR-BHET in which the amount of free ethylene glycol is controlled, and the amount of foreign matter in the resulting PET resin is also large.

[table 3] Embodiment Comparison Example Reference example 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 1 2 raw material CR-BHET1 mol% 100 85 70 50 70 60 50 100 100 100 100 100 100 CR-BHET2 mol% 100 CR-BHET3 mol% 40 50 100 TPA mol% 15 30 50 30 100 100 EG mol% 200 130 Reaction Step 1 Time minute 5 5 25 45 100 45 5 5 5 5 5 5 5 5 5 145 180 Condensation time minute 180 180 170 150 200 150 180 180 180 150 130 130 130 130 140 170 140 OLG-AV eq/t 100 90 800 1800 2300 1800 90 100 80 100 100 100 100 100 100 500 1000 OLG-OHV eq/t 7600 7400 5500 4200 2800 4100 7400 7200 9000 7600 7600 7600 7600 7600 7600 4300 2000 OH% % 98.7 98.8 87.3 70.0 54.9 69.5 98.8 98.6 99.1 98.7 98.7 98.7 98.7 98.7 98.7 89.6 66.7 Free EG mol% 0.1 0.3 0.1 0.2 0.2 0.1 1.2 1.4 1.9 0.2 0.2 0.2 0.2 0.2 0.2 2.5 1.6 Al ppm 30 30 30 30 30 15 30 30 30 30 30 P ppm 74 74 74 74 74 38 74 74 74 30 30 17 20 74 74 Sb ppm 200 700 250 Ti ppm 30 Ge ppm 115 100 Co ppm 57 _TiO2 ppm 3000 PET IV dl/g 0.589 0.599 0.592 0.596 0.591 0.593 0.591 0.594 0.596 0.595 0.602 0.589 0.599 0.602 0.591 0.603 0.594 AV eq/t 7 7 7 9 15 9 8 9 7 13 11 11 15 13 12 9 11 Foreign matter amount Pieces/ml 1100 1300 1400 1500 1600 900 1700 1800 2100 3300 2400 3000 8000 ＞10000 2300 2200 2000 Tc2 ℃ 189 192 193 192 193 184 194 196 199 202 200 202 209 204 200 198 199 b value 3.3 3.7 3.5 3.7 4.3 3.6 3.7 3.7 3.5 3.6 11.2 2.9 4.5 0.8 -0.1 4.6 4.5 After treatment IV dl/g 0.545 0.545 0.551 0.541 0.515 0.549 0.539 0.530 0.482 0.531 0.520 0.526 0.497 0.516 0.523 0.523 0.472 IV retention rate % 93 91 93 91 87 93 91 89 81 89 86 89 83 86 88 87 79

In addition, in Table 3, the molar ratio recorded in the column of CR-BHET, the raw material in the examples and comparative examples, indicates the ratio of all polycarboxylic acid components in CR-BHET when the total of all polycarboxylic acid components in CR-BHET and added terephthalic acid is set to 100 mol%; the molar ratio recorded in the column of TPA, the raw material, indicates the ratio of added terephthalic acid when the total of all polycarboxylic acid components in CR-BHET and added terephthalic acid is set to 100 mol%. In addition, in Table 3, the molar ratio recorded in the column of EG, the raw material in the reference example, indicates the ratio of ethylene glycol when the amount of terephthalic acid is set to 100 mol%. [Industrial Applicability]

The chemically recycled polyethylene terephthalate resin obtained by using chemically recycled BHET as a raw material and using an aluminum compound and a phosphorus compound as a polymerization catalyst can reduce the amount of foreign matter that is difficult to remove by a filter compared to the conventional PET resin, and can improve the processing suitability and transparency of the PET resin. The resin of the present invention is suitable for use as a material for various molded products such as optical applications, films, fibers, and beverage bottles.

Claims (7)

A chemically recycled polyethylene terephthalate resin having the following characteristics (1)-(2): (1) containing aluminum atoms and phosphorus atoms (2) the amount of foreign matter with a particle size of 0.50-0.69 μm obtained by a particle counter is less than 2000 particles/ml. The chemically recycled polyethylene terephthalate resin of claim 1, wherein the content of aluminum atoms in the chemically recycled polyethylene terephthalate resin is less than 50 mass ppm, and the content of phosphorus atoms is less than 100 mass ppm. For example, the chemically recycled polyethylene terephthalate resin of claim 1 has an inherent viscosity retention rate of 89% or more. The chemically recycled polyethylene terephthalate resin of claim 1 has a color b value of less than 10. A formed body comprising the chemically recycled polyethylene terephthalate resin of any one of claims 1 to 4. A method for producing a chemically recovered polyethylene terephthalate resin, which is a method for producing a polyethylene terephthalate resin using a raw material containing chemically recovered bis-2-hydroxyethyl terephthalate obtained by decomposing a polyester resin, and is characterized by: In the presence of an aluminum compound and a phosphorus compound, the raw material containing chemically recovered bis-2-hydroxyethyl terephthalate is directly subjected to a polycondensation reaction or is subjected to a polycondensation reaction after its OH terminal is esterified. A method for producing a chemically recycled polyethylene terephthalate resin as claimed in claim 6, wherein the amount of free ethylene glycol components in 100 mol% of all polyol components constituting the chemically recycled bis-2-hydroxyethyl terephthalate is less than 1.5 mol%.