JP2021120445A - Recycled polyester resin and method for producing recycled polyester resin - Google Patents

Abstract

To provide a recycled polyester resin that can be used in the production of various forms of polyester products, the recycled polyester resin obtained from a recycled polyester raw material derived from a used polyester product, or a recycled polyester raw material derived from scrap or the like generated in the process of producing a polyester resin or product.SOLUTION: A polyester resin contains a component derived from at least one recycled polyester raw material of a) a used polyester product and b) an unemployed polyester resin generated in the process of producing a polyester product. (1) When the total content of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less, (2) a carboxyl terminal group concentration is 30 equiv./t or less, and (3) an average pressure rise rate is 0.6 MPa/h or less.SELECTED DRAWING: None

Description

The present invention relates to a novel recycled polyester resin and a method for producing a recycled polyester resin. In particular, the present invention is produced by using a recycled polyester raw material derived from a used polyester product and a recycled polyester raw material derived from an unadopted polyester generated in the process of manufacturing the polyester product, and the amount of foreign matter mixed is small. The present invention relates to a recycled polyester resin that can be processed into various molded products in the same manner as a virgin polyester resin, and a method for producing the same.

Polyethylene terephthalate (PET) has a high melting point, chemical resistance, and a relatively low cost, so that it is widely used in molded products such as fibers, films, and PET bottles. These polyester products inevitably generate waste at the manufacturing stage or the processing stage, and are often disposed of after use. However, when incinerating, high heat is generated, so that the incinerator is severely damaged and its life is shortened. On the other hand, if it is not incinerated, it will remain semi-permanently because it will not decompose.

In recent years, among polyester products that have been used once, plastic containers that have been thrown away as garbage flow out into the ocean via rivers, are crushed into small pieces by the action of waves or tidal currents, and accumulate in the body of marine organisms as microplastics. Since it is concentrated in the food chain and has an adverse effect on the ecosystem of marine organisms, and that plastics are a major cause of marine pollution, it is regarded as a problem. Movements such as switching to are occurring all over the world.

From the viewpoint of such environmental problems, recycling that reuses resources is carried out by various methods. For polyester products such as PET, in addition to the method of recycling polyester waste generated in the manufacturing process, a method of collecting discarded products once on the market and reusing them as raw materials has been studied. There is. In particular, in recent years, textile products with the Eco Mark, which is certified by achieving a certain recycling rate, have become widespread.
As a recycled polyester raw material, various methods have been proposed as a method of recycling using a polyester waste generated in a manufacturing process or a recovered polyester product.

For example, a method of adding methanol to PET waste and decomposing it into dimethylene terephthalate (hereinafter sometimes referred to as "DMT") and ethylene glycol (hereinafter sometimes referred to as "EG") (Patent Document 1). ), A method in which EG is added to PET waste to depolymerize it, and then methanol is added to recover DMT (Patent Document 2). PET waste is depolymerized with EG to form an oligomer, which is used in a polycondensation reaction. A method (Patent Document 3) and the like have been proposed.

By the way, as impurities that become a problem when regenerating PET bottles and the like once become products, in addition to various additives added in polyester resin, a) cap (aluminum) is attached to the bottle body. , Polypropylene, polyethylene), b) Inner plug, c) Liner (polypropylene, polyethylene), d) Label (paper, resin such as polystyrene, ink), e) Adhesive, f) Printing ink and the like.

Generally, as a pretreatment in the regeneration step, the collected PET bottle is subjected to a vibrating sieve to remove sand, metal and the like. Then, the PET bottle is washed, the colored bottle is separated, and then rough crushing is performed. Then, the label and the like are removed by wind power separation. Further, the PET bottle piece is finely crushed except for the aluminum piece derived from the cap or the like. A step of removing components such as adhesives, proteins, and molds by high-temperature alkaline cleaning and separating dissimilar components such as polypropylene and polyethylene by the difference in specific densities is performed.

However, even through these steps, it is difficult to completely separate and remove non-polyester resins such as polypropylene, polyethylene, and polystyrene from PET resins.

For example, even if an attempt is made to produce a recycled polyester resin by the recycling method described in Patent Documents 1 to 4, foreign matter derived from a non-polyester resin cannot be sufficiently removed, and the amount of foreign matter mixed can be sufficiently reduced. However, it is difficult to obtain a product having the same quality as the virgin polyester resin. If the amount of foreign matter mixed in is not sufficiently reduced in this way, the pressurizing speed of the filtration filter in the spinning process or the film forming process is high, continuous operation for a long period of time cannot be performed, and processing operability is extremely deteriorated. Moreover, the methods described in Patent Documents 1 to 3 require a large amount of cost for installation, operation, maintenance, and the like of the recovery device, and there is room for improvement in terms of practicality.

Special Publication No. 42-8855 Japanese Unexamined Patent Publication No. 48-62732 Japanese Unexamined Patent Publication No. 60-248646 Japanese Unexamined Patent Publication No. 2005-171138

In this way, not only various inorganic substances but also foreign substances derived from non-polyester resins are sufficiently removed, and a method for obtaining a recycled polyester resin capable of obtaining various products in the same manner as the virgin polyester resin is still being developed. Has not been reached.

In particular, when melt spinning is performed using a polyester resin to produce fibers, the amount of foreign matter mixed in has a great influence on productivity. When manufacturing fibers, the resin is extruded from a nozzle with a small pore diameter in the melt spinning process, a large number of extruded filaments are taken up by a roller, and if necessary, a drawing or heat treatment process is performed, and a winding process is performed. Go through. In this case, if a resin mixed with a foreign substance is used, trouble of yarn breakage is likely to occur in any of the melt spinning, drawing / heat treatment, and winding steps, and it becomes difficult to carry out stable production.

This problem becomes more pronounced when trying to produce finer fibers. For example, in a recycled polyester resin produced by using polyester waste or the like as a raw material, it has not yet been realized to obtain ultrafine fibers having a single yarn fineness of 0.5 decitex or less by melt spinning.

Therefore, a main object of the present invention is to solve the above-mentioned problems and to obtain a recycled polyester raw material derived from a used polyester product, or a recycled polyester raw material derived from polyester resin and scraps generated in the process of manufacturing the product. As a raw material, it is an object of the present invention to provide a recycled polyester resin that can be used for producing various forms of polyester products.

As a result of intensive research in view of the problems of the prior art, the present inventor has found that a polyester resin obtained by treating with a recycled polyester raw material in a specific step can achieve the above object, and has developed the present invention. It came to be completed.

That is, the present invention relates to the following recycled polyester resin and a method for producing the same.
1. 1. A polyester resin containing components derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resins generated in the process of manufacturing polyester products.
(1) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less.
(2) The carboxyl terminal group concentration is 30 equivalents / t or less, and
(3) The average boosting speed is 0.6 MPa / h or less (however, the average boosting speed is a value calculated by the following procedure: using a boosting tester including an extruder and a pressure sensor, the extruder Stainless steel filter at the tip (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size : 12 μm) is set, the polyester resin is melted at 300 ° C. with an extruder, and the extruding is started as the pressure value applied to the filter when the melt is extruded at a discharge rate of 29.0 g / min from the filter. If the pressure value at that time is the "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is the "final pressure value (MPa)", the following calculation is performed based on those pressure values. The above average boosting speed is calculated by the formula A:
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12) ... A),
Recycled polyester resin characterized by this.
2. The fiber containing the recycled polyester resin according to Item 1.
3. 3. A blow-molded product containing the recycled polyester resin according to Item 1.
4. The film containing the recycled polyester resin according to Item 1.
5. A method for producing a recycled polyester resin using at least one recycled polyester raw material of unadopted polyester generated in the process of producing a used polyester product and b) a polyester product.
(1) The raw material is added to a mixture containing an ethylene terephthalate oligomer and ethylene glycol so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35, and heat treatment is performed at 245 to 280 ° C. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under conditions,
(2) A step of collecting the filtrate by passing the reaction product through a filter having a filtration particle size of 10 to 25 μm.
(3) A method for producing a regenerated polyester resin, which comprises a step of adding a polymerization catalyst to the filtrate and carrying out a polycondensation reaction of the depolymerized product under a reduced pressure of 260 ° C. or higher and 1.0 hPa or lower.
6. Item 5. The production method according to Item 5, wherein the raw material contains at least 40% by mass or more of a) a used polyester product and b) at least one of unadopted polyester resins generated in the process of producing the polyester product.

According to the present invention, various forms of polyester products are manufactured from recycled polyester raw materials derived from used polyester products, or recycled polyester raw materials derived from polyester resins and polyester scraps generated in the process of manufacturing the products. It is possible to provide a recycled polyester resin that can be used for.

In particular, in the present invention, a) a used polyester product and b) at least one recycled polyester raw material of unadopted polyester generated in the process of manufacturing the polyester product is used in a high ratio, and the amount of foreign matter mixed is small. Moreover, it is possible to provide a regenerated polyester resin in which the carboxyl terminal group concentration and the diethylene glycol content are controlled within a specific range. As a result, for example, in the process of obtaining fibers by melt spinning, the process of obtaining sheets or films by film forming, and the process of obtaining molded products such as bottles, continuous operation for a relatively long period of time becomes possible, and products of various forms with good productivity are possible. Can be manufactured.

In addition, the products (fibers, sheets, films, bottles, etc.) obtained from the recycled polyester resin of the present invention have high thermal stability and excellent heat resistance, and are as excellent as those using the virgin polyester resin. You can demonstrate the quality.

According to the method for producing a recycled polyester resin of the present invention, it is possible to efficiently and reliably produce a recycled polyester resin having a small amount of foreign matter mixed in, high thermal stability, and excellent heat resistance as described above. It will be possible.

1. 1. Recycled Polyester Resin The recycled polyester resin of the present invention (resin of the present invention) contains components derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyesters generated in the process of manufacturing polyester products. It is a polyester resin containing
(1) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less.
(2) The carboxyl terminal group concentration is 30 equivalents / t or less, and
(3) The average boosting speed is 0.6 MPa / h or less (however, the average boosting speed is a value calculated by the following procedure: using a boosting tester including an extruder and a pressure sensor, the extruder Stainless steel filter at the tip (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size : 12 μm) is set, the polyester resin is melted at 300 ° C. with an extruder, and the extruding is started as the pressure value applied to the filter when the melt is extruded at a discharge rate of 29.0 g / min from the filter. If the pressure value at that time is the "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is the "final pressure value (MPa)", the following calculation is performed based on those pressure values. The above average boosting speed is calculated by the formula A:
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12) ... A)
It is characterized by that.

The resin component constituting the resin of the present invention includes a) a used polyester product and b) a component derived from at least one recycled polyester raw material of unadopted polyester generated in the process of manufacturing the polyester product. These components are a part of the polyester constituting the resin of the present invention.

Examples of the used polyester product in a) above include polyester molded products (including fibers) that have been put on the market once and collected after use. A typical example thereof is a container or packaging material such as a PET bottle.

The unadopted polyester generated in the process of manufacturing the polyester product of b) above is a polyester that has not been commercialized, for example, non-standard resin pellets, materials that are no longer needed during molding, and fragments cut during molding. , Scraps (polyester scraps) generated during molding, processing, etc., cut products of transition products generated when changing brands, cut products of prototypes / defective products, etc. can be mentioned.

The forms of a) and b) are not limited, and they may be pelletized by further processing such as crushing or cutting as necessary, or they may be melted and pelletized. good. The above a) and b) may be used alone or a mixture of both may be used.

Further, the recycled polyester raw materials of a) and b) may be either crystalline or amorphous. Therefore, for example, pellets of amorphous polyester waste that have not been heat-treated, crystalline pellets that have been heat-treated, and a mixture of crystalline pellets and amorphous pellets can be used. In the present invention, it is preferable to use a crystalline recycled polyester raw material for the purpose of preventing fusion of pellets to each other, particularly during charging into a can, depolymerization reaction, and the like. Therefore, the material of the above a) or b) crystallized by heat treatment (crystallized pellets or the like) can be preferably used.

Further, the properties of the recycled polyester raw materials of the above a) and b) are not limited, and the forms of the above a) and b) may be used as they are, and a cutting fragment obtained by further processing such as cutting and crushing may be performed. In addition to crushed products (powder) and the like, solid forms such as molded products (pellets and the like) obtained by molding these can be mentioned. More specifically, pellets obtained by cooling and cutting a melt of polyester waste, cut fragments obtained by finely cutting a polyester molded product such as a PET bottle, and the like are exemplified. In addition, it may be in the form of a liquid (dispersion liquid or solution) obtained by dispersing or dissolving the above-mentioned cut pieces, pulverized product (powder) or the like in a solvent. When producing polyester products using these raw materials, if necessary, they can be melted at a temperature equal to or higher than the melting point and put into a can as a melt.

The recycled polyester resin of the present invention (resin of the present invention) contains components derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyesters generated in the process of manufacturing polyester products. The content of the component is preferably 40% by mass or more, and more preferably 50% by mass or more in the resin of the present invention. If the content is less than 40% by mass, the recycling rate of the unadopted polyester decreases. The upper limit of the content is not particularly limited, but according to the production method of the present invention described later, it is possible to easily obtain a recycled polyester resin having a content of 40 to 80% by mass of a recycled polyester raw material. Is.

When the total amount of all glycol components in the resin of the present invention is 100 mol%, the content of diethylene glycol is 4 mol% or less, and more preferably 3.5 mol% or less. In particular, in the resin of the present invention obtained by the production method of the present invention, ethylene glycol is used as one of the raw materials, and diethylene glycol may be produced as a by-product at that time. The resin of the present invention has a small amount of diethylene glycol produced as a by-product, and excellent thermal stability can be obtained by setting the content of diethylene glycol to 4 mol% or less. Therefore, it is possible to obtain molded products such as fibers, injection molded products, various blow molded products, sheets, and films with high productivity. The lower limit of the content of diethylene glycol can be, for example, about 0.5 mol%, but is not limited to this.

The resin of the present invention has a carboxyl-terminal group concentration of 30 equivalents / t or less, particularly preferably 25 equivalents / t or less, and most preferably 20 equivalents / t or less. By setting the carboxyl-terminal group concentration to 30 equivalents / t or less, it has excellent heat resistance, and it is possible to obtain a molded product having excellent heat resistance by various molding methods. The lower limit of the carboxyl terminal group concentration can be, for example, about 5 equivalents / t, but is not limited to this.

The resin of the present invention has an average step-up rate of 0.6 MPa / h or less, preferably 0.5 MPa / h or less, and more preferably 0.4 MPa / h or less, as measured by the following method. .. The average boosting speed in the present invention is an index of a large amount of foreign matter derived from various inorganic substances, foreign matter derived from non-polyester resin, etc., and the smaller the average boosting speed, the smaller the amount of foreign matter mixed. Is shown. Since the average step-up rate is 0.6 MPa / h or less, it is possible to produce ultrafine fibers having a single yarn fineness of 0.5 decitex or less by, for example, melt spinning. The lower limit of the average boosting speed can be, for example, about 0.01 MPa / h, but is not limited to this.

The average boosting speed is measured by using a boosting tester including an extruder and a pressure sensor, setting the filter at the tip of the extruder, melting the polyester resin at 300 ° C. with the extruder, and discharging from the filter. As the pressure value applied to the filter when the melt is extruded at an amount of 29.0 g / min, the pressure value at the start of extruding is set to "initial pressure value (MPa)", and then continuously extruded for 12 hours. When the pressure value of is set to "final pressure value (MPa)", the average boosting speed is calculated by the following formula A based on those pressure values:
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12) ... A)
It is by the method.

As the extruder, filter, etc. used in the above measurement, known or commercially available ones can be appropriately used as long as the provisions of the present invention are satisfied.

In the present invention, if necessary, as shown in the test example described later, a reinforcing material may be added to the filter within a range that does not substantially affect the measurement result. In the above measurement method, an extremely high pressure is applied to the filter, so that the filter alone may be deformed or damaged. In such cases, it is preferable to support the filter with a reinforcing material. As the reinforcing material, a mesh-like metal member or the like can be used. More specifically, a metal filter having a strength capable of preventing deformation of the filter and having a coarse mesh that does not substantially affect the measurement result can be preferably used as the reinforcing material. Then, such a reinforcing material can be used by laminating it on the downstream side of the filter.

The type of the resin of the present invention is not limited as long as it is a polyester resin, but it is preferable that the resin is mainly composed of polyethylene terephthalate (PET). The content of PET in the regenerated polyester resin of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90 to 100% by mass. Therefore, for example, a recycled polyester resin having a PET content of 95 to 99% by mass is also included in the present invention.

In particular, in the production method of the present invention described later, PET, which is a polycondensate of ethylene glycol and terephthalic acid, can usually be obtained, but when a component other than ethylene glycol and terephthalic acid is present in the recycled polyester raw material. In some cases, a polyester resin other than PET is produced by a polycondensation reaction. Therefore, in the resin of the present invention, in addition to the main PET, the following components may be copolymerized as an acid component or a glycol component. Two or more of these components may be contained.

Examples of the acid component include isophthalic acid, phthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, dodecanedioic acid and the like, dimer acid, and trimellitic anhydride, tri. Examples thereof include merit acid, pyromellitic acid, 1,4-cyclohexanedicarboxylic acid, sebacic acid and dimer acid.

Examples of the glycol component include neopentyl glycol, 1,4-butanediol, 1,2-propylene glycol, 1,5-pentanediol, 1,3-propanediol, 1,6-hexamethylenediol, diethylene glycol, and 1, Examples thereof include 4-cyclohexanedimethanol, dimerdiol, butylethylpropanediol, (2-methyl1,3-propanediol, trimethylolpropane, glycerin, pentaerythritol, bisphenol A or an ethylene oxide adduct of bisphenol S).

2. Method for Producing Recycled Polyester Resin The method for producing the resin of the present invention is not limited, but the resin of the present invention can be suitably produced by, for example, the following production method. That is, it is a method for producing a recycled polyester resin using at least one recycled polyester raw material of a) used polyester product and b) unadopted polyester generated in the process of producing the polyester product.
(1) The raw material is added to a mixture containing an ethylene terephthalate oligomer and ethylene glycol so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35, and heat treatment is performed at 245 to 280 ° C. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under conditions (depolymerization step).
(2) A step of passing the reaction product through a filter having a filtration particle size of 10 to 25 μm to recover the filtrate (filtration step).
(3) A step of adding a polymerization catalyst to the filtrate and carrying out a polycondensation reaction of the depolymerized product under a reduced pressure of a temperature of 260 ° C. or higher and 1.0 hPa or lower (polycondensation step).
A method for producing a recycled polyester resin, which comprises the above, can be preferably adopted. In other words, as the recycled polyester resin of the present invention, the recycled polyester resin obtained by the above-mentioned manufacturing method of the recycled polyester resin can be preferably adopted.

Depolymerization Step In the depolymerization step, the raw material is added to a mixture containing an ethylene terephthalate oligomer and ethylene glycol so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35, and 245. A reaction product containing the depolymerized product is obtained by performing depolymerization under heat treatment conditions of about 280 ° C.

As the ethylene terephthalate oligomer and ethylene glycol, known or commercially available ones can be used. It can also be produced by a known production method.

In particular, as the ethylene terephthalate oligomer, for example, an esterification reaction product of ethylene glycol and terephthalic acid can be preferably used. The number average degree of polymerization of the ethylene terephthalate oligomer is not limited, but can be, for example, about 2 to 20.

The amount of the ethylene terephthalate oligomer used is not particularly limited, but is preferably about 0.20 to 0.80% by mass, particularly 0.30 to 0.70% by mass, based on 100% by mass of the finally obtained recycled polyester resin. It is more preferable to set it to%. If the amount of the ethylene terephthalate oligomer is smaller than the above, when the recycled polyester raw materials are added, the recycled polyester raw materials are likely to cause blocking, which may impose an excessive load on the stirrer. On the other hand, when the amount of the ethylene terephthalate oligomer is larger than the above range, there is no particular problem in the depolymerization reaction, but the recycling rate of the finally obtained recycled polyester resin may be low.

The amount of ethylene glycol added is preferably 5 to 15 parts by mass with respect to 100 parts by mass of the ethylene terephthalate oligomer from the viewpoint of sufficiently advancing the depolymerization reaction, and among them, 10 to 15 parts by mass. Is more preferable. If the amount of ethylene glycol added exceeds 15 parts by mass, the ethylene terephthalate oligomer tends to solidify in the reactor, and the subsequent reaction may not be continued.

The mixing of the ethylene terephthalate oligomer and the ethylene glycol is not particularly limited, but it is preferable to add ethylene glycol to the ethylene terephthalate oligomer, for example. Further, when adding the oligomer, it is preferable to make the temperature of the content uniform while rotating the stirrer for the purpose of preventing the oligomer from solidifying.

To the mixture of ethylene terephthalate oligomer and ethylene glycol, at least one recycled polyester raw material of a) used polyester product and b) unemployed polyester generated in the process of producing the polyester product is added. Specific examples of the above a) and b) include the above 1. You can use the same ones listed in.

When the recycled polyester raw material is added, it is preferable to carry out the process while stirring under normal pressure, and it is more preferable to add the recycled polyester raw material in a state of being purged with a small amount of inert gas (generally, nitrogen gas is used). As a result, it is possible to prevent the mixing of oxygen and more reliably prevent the deterioration of the color tone.

The polyester raw material is added so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35. The molar ratio is particularly preferably 1.10 to 1.33, and more preferably 1.12 to 1.30. When the molar ratio of the total glycol component / total acid component is out of the above range, the obtained recycled polyester resin does not satisfy at least one of the carboxyl terminal group concentration and the diethylene glycol content specified in the present invention, and the average The boost speed also increases. This is because when the molar ratio of the total glycol component / total acid component when performing the depolymerization reaction is out of the above range, foreign substances derived from various inorganic substances and non-polyester resins are not efficiently precipitated, and thus the filtration step. As a result, these foreign substances cannot be effectively filtered, and the foreign substances tend to precipitate after the polycondensation step, resulting in a regenerated polyester resin having a high average step-up rate.

In the production method of the present invention, the depolymerization step is particularly important. That is, in the conventional method using the recycled polyester raw material, depolymerization is performed using only the recycled polyester raw material, whereas in the present invention, the solution of the recycled polyester raw material is performed in the presence of ethylene terephthalate oligomer and ethylene glycol. The polymerization reaction is carried out, and the recycled polyester raw material is added so that the molar ratio of the total glycol component / total acid component is within the above range for all the components of the oligomer, ethylene glycol and the recycled polyester raw material, and the depolymerization reaction is carried out. .. By doing so, not only various inorganic substances but also foreign substances derived from non-polyester resin are efficiently deposited, so that these foreign substances can be effectively filtered in the filtration step described later. Then, in the polycondensation step described later, it is possible to obtain a recycled polyester resin having a diethylene glycol content and a carboxyl-terminal group concentration of a specific amount or less and a relatively small amount of foreign matter mixed. In the production method of the present invention, it is desirable that the recycled polyester raw material is not decomposed into monomers but decomposed into oligomers having a repeating unit of about 5 to 20 by the above-mentioned depolymerization reaction. By controlling in this way, not only various inorganic substances but also foreign substances derived from non-polyester resin are efficiently deposited, and as a result, more foreign substances can be removed.

In the depolymerization step, the reaction temperature at the time of depolymerization (particularly the internal temperature of the reactor) is preferably set in the range of 245 to 280 ° C., and among them, the reaction temperature is set in the range of 255 to 275 ° C. More preferred. When the reaction temperature at the time of depolymerization is less than 245 ° C., the reactants solidify and the operability deteriorates, and even if a recycled polyester resin is obtained, the diethylene glycol content or the carboxyl terminal group concentration is high. It tends to be too much. If the reaction temperature exceeds 280 ° C., the diethylene glycol content or the carboxyl-terminal group concentration of the obtained regenerated polyester resin may become too high.

The reaction time for depolymerization (reaction time after the completion of charging of the recycled polyester raw material) is not particularly limited, but is usually preferably within 4 hours, and in particular, suppressing the by-product amount of diethylene glycol and polyester. It is more preferable that the time is within 2 hours from the viewpoint of suppressing deterioration of color tone. The lower limit of the reaction time is not limited, and may be, for example, about 1 hour.

The reaction apparatus used in the production method of the present invention is not particularly limited, and known or commercially available apparatus can also be used. In particular, even in the reactor, the capacity, the shape of the stirring blade, etc. are not particularly problematic in the generally used esterification reactor, but ethylene glycol is distilled out of the system in order to efficiently proceed with the depolymerization reaction. It is preferable that the reactor has a structure in which a distillation column is provided so as not to allow the reaction.

Filtration process
In the filtration step, the reaction product is passed through a filter having a filtration particle size of 10 to 25 μm to collect the filtrate.

The reaction product obtained in the above-mentioned depolymerization step is a liquid material mainly containing the depolymerization of the polyester raw material. In the filtration step, the liquid material is passed through a filter having a filtration particle size of 10 to 25 μm to filter foreign substances, and the filtrate is collected. In the depolymerization step, not only various inorganic substances but also foreign substances derived from non-polyester resin are efficiently precipitated. Therefore, the precipitated foreign substances are filtered by passing through a filter having a filtration particle size of 10 to 25 μm to filter the foreign substances. It is possible to obtain a depolymerized product in which the amount of the mixture is small. If a filter having a filtration particle size larger than 25 μm is used, the foreign matter in the polymer cannot be sufficiently removed, and the amount of foreign matter in the obtained recycled polyester resin increases. Therefore, when spinning is performed using such a resin, the pressure of the nozzle pack is increased or the yarn is cut. On the other hand, if a filter having a filtration particle size smaller than 10 μm is used, clogging due to foreign matter is likely to occur, and the filter life is shortened, which is disadvantageous in terms of cost and may reduce operability.

As the filter that can be used in the filtration step, a general filter is not particularly problematic, but a metal filter is particularly preferable. Examples of the material include stainless steel and the like. The filter type is also not particularly limited, and examples thereof include a screen changer type filter, a leaf disc filter, and a candle type sintered filter. As these, known or commercially available ones can be used.

Polycondensation step In the polycondensation step, a polycondensation catalyst is added to the filtrate, and the polycondensation reaction of the depolymerized product is carried out under reduced pressure of a temperature of 260 ° C. or higher and 1.0 hPa or lower.

As the polycondensation catalyst, for example, at least one of a germanium compound, an antimony compound, a titanium compound, a cobalt compound and the like can be used. Among them, at least one of a germanium compound and an antimony compound is used in particular. When the transparency of the obtained recycled polyester resin is important, it is preferable to use a germanium compound. Examples of the above compounds include oxides such as germanium, antimony, titanium and cobalt, inorganic acid salts, organic acid salts, halides and sulfides.

^{The amount of the polycondensation catalyst used is not particularly limited, but is preferably 5 × 10 -5} mol / unit or more with respect to 1 mol of the acid component of the polyester resin to be produced, and among them, 6 × 10 ^-5 mol / unit. It is more preferable that the content is unit or more. The upper limit of the amount used can be, for example, about 1 × 10 ^-3 mol / unit, but is not limited thereto.

Since the polymerization catalyst contained in the recycled polyester raw material may also act as a catalyst during the polycondensation reaction, the type of polymerization catalyst contained in the recycled polyester raw material is used when the polymerization catalyst is added in the polycondensation step. And its content are preferably taken into account.

Further, at the time of the polycondensation reaction, if necessary, the fatty acid ester, the hindered phenolic antioxidant, and the resin, which can adjust the melt viscosity, can be suppressed from thermal decomposition in combination with the above polycondensation catalyst. A phosphorus compound can also be added.

Examples of the fatty acid ester include beeswax (a mixture containing myricyl palmitate as a main component), stearyl stearate, behenyl behenate, stearyl behenate, glycerin monopalmitate, glycerin monostearate, glycerin disstearate, and glycerin tri. Examples thereof include stearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate. Among these, glycerin monostearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate are preferable. These can be used alone or in combination of two or more.

Examples of the hindered phenol-based antioxidant include 2,6-di-t-butyl-4-methylphenol and n-octadecyl-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl). ) Propionate, tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 4 , 4'-butylidenebis- (3-methyl-6-t-butylphenol), triethylene glycol-bis [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate], 3,9-bis {2- [3- (3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1'-dimethylethyl} -2,4,8,10-tetraoxaspiro [5,5 ] Undecane and the like are used, but tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane is preferable in terms of effectiveness and cost. These can be used alone or in combination of two or more.

As the phosphorus compound, for example, phosphorus compounds such as phosphorous acid, phosphoric acid, trimethylphosphine, triphenylphosphine, tridecylphosphine, trimethylphosphate, tridecylphosphine, and triphenylphosphine can be used. These can be used alone or in combination of two or more.

In the polycondensation reaction, the polycondensation reaction is carried out under a reduced pressure of a temperature of 260 ° C. or higher and 1.0 hPa or lower. If the polycondensation reaction temperature is less than 260 ° C., or if the pressure during the polycondensation reaction exceeds 1.0 hPa, the polycondensation reaction time becomes long, resulting in poor productivity. The polycondensation reaction temperature is more preferably 270 ° C. or higher. However, if the polycondensation reaction temperature is too high, the polymer is colored by thermal decomposition and the color tone is deteriorated, and the amount of terminal groups (COOH) is also increased by thermal decomposition. Therefore, in the present invention, the upper limit of the polycondensation reaction temperature is generally preferably 285 ° C. or lower.

The ultimate viscosity of the regenerated polyester resin of the present invention obtained by the above polycondensation reaction is not particularly limited, but is usually preferably about 0.44 to 0.80. Further, the regenerated polyester resin of the present invention can also be used for molding applications by increasing the degree of polymerization through a solid phase polymerization step, as will be described later. In this case, the ultimate viscosity of the obtained recycled polyester resin is preferably 0.80 to 1.25.

Crystallization Step In the present invention, the polyester resin obtained above can be further subjected to a crystallization step, if necessary. Thereby, the crystallinity of the polyester resin can be enhanced.

The crystallization conditions are not particularly limited, but can be carried out, for example, by performing heat treatment at the crystallization temperature of the polyester resin used or higher. For example, when the polyester resin is PET, the crystallization temperature of PET is usually about 130 ° C., so that the heat treatment can be performed at a temperature of, for example, 135 ° C. or higher (preferably 140 to 180 ° C.). The heat treatment time can be changed depending on the heat treatment temperature and the like, and can be, for example, about 30 minutes to 20 hours, but is not limited to this.

Solid-Phase Polymerization Step In the present invention, if necessary, the resin obtained in the polycondensation step or the crystallization step can be further subjected to a solid-phase polymerization reaction. As a result, the recycled polyester resin can be made more suitable for molding by further increasing the degree of polymerization.

The conditions of the solid-phase polymerization reaction are not limited, but the heat treatment may be carried out so that the ultimate viscosity of the obtained recycled polyester resin is 0.80 to 1.25 (particularly 0.82 to 1.24). preferable. More specifically, for example, it can be carried out by heat-treating the resin obtained in the polycondensation step or the crystallization step at about 180 to 240 ° C. in an inert gas atmosphere. The heat treatment time depends on the heat treatment temperature and the like, but is usually about 5 to 50 hours.

3. 3. Use of Recycled Polyester Resin The resin of the present invention can be used in the production of various products as it is or after being mixed with other additives as needed to form a resin composition.

As the additive, as long as the effect of the present invention is not impaired, in addition to the above-mentioned additives such as polymerization catalysts, antioxidants and phosphorus compounds, colorants, pigments, dispersants, fillers and ultraviolet absorbers. , Thickeners, antistatic agents, anticoloring agents, stabilizers, flame retardants, lubricants and the like.

In particular, a colorant can also be preferably used. For example, phosphorus compounds such as phosphorous acid, phosphoric acid, trimethylphosphine, triphenylphosphine, tridecylphosphine, trimethylphosphate, tridecylphosphate, and triphenylphosphine can be used. These phosphorus compounds may be used alone or in combination of two or more.

Further, in order to suppress coloring due to thermal decomposition of the polyester resin, additives such as a cobalt compound such as cobalt acetate, a manganese compound such as manganese acetate, an anthraquinone dye compound, and a copper phthalocyanine compound may be contained.

As various products, the same forms as those of conventional polyester products can be adopted. As the polyester product, for example, it can be suitably used in the form of fibers, molded products, films and the like.

In the case of fibers, for example, fibers can be produced by a production method including a step of melting and spinning a raw material containing the resin of the present invention. This makes it possible to produce, for example, ultrafine fibers having a single yarn fineness of 0.8 decitex or less (preferably 0.6 to 0.3 decites). The spinning method and the like can be carried out according to known conditions.

As described above, the resin of the present invention has a relatively low content of foreign matter and has the same characteristics as the virgin polyester resin. Is less likely to occur, and polyester fibers can be obtained with good productivity.

The fiber of the present invention containing the resin of the present invention may be, for example, any of monofilaments, multifilaments and the like, and may be any of long fibers, short fibers and the like. In the production of fibers, it is generally more difficult to produce a multifilament, but in the fiber of the present invention, for example, a single yarn fineness of 0.3 to 30 decitex, a single yarn number of 2 to 300, and a total fineness of 5 to 350 A multifilament having a strength of 1 to 5 cN / decitex and a characteristic value of an elongation of 10 to 400% can be obtained. Among them, ultrafine fibers, which are more difficult to manufacture, can also be obtained.

In the case of a molded product, it can be manufactured, for example, by applying various molding methods such as press molding, extrusion molding, compressed air molding, and blow molding using a raw material containing the resin of the present invention. Thereby, various parts such as a container can be provided. The resin of the present invention has properties similar to those of a virgin polyester resin and is excellent in thermal stability, and is therefore particularly suitable for producing blow-molded products. Therefore, a method for producing a molded product including a step of obtaining a parison from a melt containing the resin of the present invention and a step of blowing gas into the parison can be preferably adopted. This makes it possible to manufacture a molded product such as a container.

In the case of a film, it can be molded by a known film forming method using a raw material containing the resin of the present invention. For example, the melt of the raw material is extruded from a T-die and then cooled with a casting roll to prepare an unstretched sheet. Since the resin of the present invention has a relatively low content of foreign matter and is excellent in thermal stability, it can be stretched in the MD and TD directions with good operability. As the stretching method, either uniaxial stretching or biaxial stretching may be used, and as the biaxial stretching method, either simultaneous biaxial stretching or sequential biaxial stretching can be adopted. Then, it is possible to obtain a polyester film having characteristic values such as strength and elongation which are almost the same as those in the case of using a virgin polyester resin and having excellent transparency.

The thickness of the film is not limited, but can usually be appropriately set within the range of 10 to 50 μm. Further, if necessary, it can be laminated with other layers (for example, an adhesive layer, a heat seal layer, a surface protection layer, a printing layer, a design layer, etc.) and used as a laminate, and the laminate can be molded. By doing so, it can be used as various molded bodies as described above.

Examples and comparative examples are shown below, and the features of the present invention will be described more specifically. However, the scope of the present invention is not limited to the examples.

A. About recycled polyester resin
Example 1
A slurry of terephthalic acid (TPA) and ethylene glycol (EG) (TPA / EG molar ratio = 1 / 1.6) is supplied to the esterification reactor and reacted at a temperature of 250 ° C. and a pressure of 50 hPa for esterification. An ethylene terephthalate oligomer having a reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the esterification reactor, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the esterification reactor was rotated. From the point where the internal temperature of the esterification reactor (hereinafter referred to as "ES can") stopped dropping, 55.0 parts by mass of recycled polyester raw material (pellet-like polyester waste generated in the process of manufacturing polyester resin) The product) was charged in a fixed amount over about 2 hours via a rotary valve.
At this time, the recycled polyester raw material was added so that the molar ratio of the total glycol component / total acid component (hereinafter, may be referred to as “G / A”) was 1.20. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product is pressure-fed to the polycondensation reactor (hereinafter referred to as PC can) by setting a candle filter having an opening of 20 μm between the esterification reactor and the polycondensation reactor, and then polymerizing. Antimon trioxide was added as a catalyst to 1.0 × 10 ^-4 mol / unit, EG slurry of titanium dioxide was added to 0.20% by mass, and the PC can was depressurized to a final pressure of 0.5 hPa and temperature 60 minutes later. A melt polymerization reaction was carried out at 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Example 2
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained. 45.0 parts by mass of ethylene terephthalate oligomer was charged into an ES can, and then 7.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the point where the internal temperature of the ES can stopped, 55.0 parts by mass of recycled polyester raw material (PET bottle crushed or remelted and pelletized) was quantitatively charged via a rotary valve over about 2 hours. ..
At this time, the recycled polyester raw material was added so that the G / A was 1.16. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, titanium dioxide EG slurry to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, carry out a melt polymerization reaction at a final pressure of 0.5 hPa and a temperature of 275 ° C. for 4 hours to regenerate. A polyester resin (extreme viscosity: 0.64) was obtained.

Example 3
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
55.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 15.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 45.0 parts by mass of recycled polyester raw material (similar to that in Example 1) was quantitatively charged over about 2 hours via a rotary valve.
At this time, the recycled polyester raw material was added so that the G / A was 1.33. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} In addition to the mol / unit, the PC can was depressurized and 60 minutes later, a melt polymerization reaction was carried out at a final pressure of 0.5 hPa and a temperature of 275 ° C. for 2 hours to obtain a regenerated polyester resin (extreme viscosity: 0.46). rice field.

Example 4
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
30.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 7.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the point where the internal temperature drop of the ES can stopped, 70.0 parts by mass of recycled polyester raw material (similar to that in Example 1) was quantitatively charged through a rotary valve over about 2 hours.
At this time, the recycled polyester raw material was added so that the G / A was 1.10. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} In addition to the mol / unit, the PC can was depressurized and 60 minutes later, a melt polymerization reaction was carried out at a final pressure of 0.5 hPa and a temperature of 275 ° C. for 5 hours to obtain a regenerated polyester resin (extreme viscosity: 0.65). rice field.

Example 5
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester raw material (similar to that in Example 1) was quantitatively charged over about 2 hours via a rotary valve.
At this time, the recycled polyester raw material was added so that the G / A was 1.20. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 250 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.30% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 280 ° C. for 6 hours to obtain a regenerated polyester resin (extreme viscosity: 0.82).

Example 6
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester was quantitatively charged through a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.20.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 25 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.05% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 280 ° C. for 3 hours to obtain a regenerated polyester resin (extreme viscosity: 0.56).

Example 7
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester was quantitatively charged through a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.20.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 15 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.05% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 280 ° C. for 2 hours to obtain a regenerated polyester resin (extreme viscosity: 0.50).

Example 8
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester was quantitatively charged through a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.20.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 10 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.05% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 280 ° C. for 5 hours to obtain a regenerated polyester resin (extreme viscosity: 0.75).

Example 9
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester was quantitatively charged through a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.20.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.05% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 260 ° C. for 7 hours to obtain a regenerated polyester resin (extreme viscosity: 0.61).

Comparative Example 1
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
30.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 2.5 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the point where the internal temperature drop of the ES can stopped, 70.0 parts by mass of recycled polyester was quantitatively charged via a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.06.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Comparative Example 2
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
50.0 parts by mass of ethylene terephthalate oligomer was charged into an ES can, and then 19.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 50.0 parts by mass of recycled polyester was quantitatively charged via a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.36.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Comparative Example 3
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into an ES can, and then 7.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester was quantitatively charged via a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.16.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 290 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Comparative Example 4
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into an ES can, and then 10.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester raw material was quantitatively charged through a rotary valve over about 2 hours. At this time, a recycled polyester raw material (similar to that in Example 1) was added so that the G / A was 1.20.
Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can with a candle filter having an opening of 30 μm set between the ES can and the PC can, and then antimony trioxide was used as a polymerization catalyst 0.7 × 10 ^-4. Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Comparative Example 5
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
48.8 parts by mass of recycled polyester raw material (similar to Example 1) was charged into an ES can, then 19.2 parts by mass of ethylene glycol was added, and a depolymerization reaction was carried out for 4 hours under heat treatment conditions at 250 ° C. went. The molar ratio of the total glycol component / total acid component during this depolymerization reaction was 1.59.
Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter having an opening of 20 μm between the ES can and the PC can, and then 51.2 parts by mass of ethylene terephthalate oligomer was charged into the PC can. , Mixed with the above-mentioned depolymerizer. At this time, the recycled polyester raw material was added so that the G / A was 1.37.
Then, as a polymerization catalyst, antimony trioxide ^{was added at 1.0 × 10 -4} mol / unit, cobalt acetate ^{was added at 0.5 × 10 -4} mol / unit, and an EG slurry of titanium dioxide was added at 0.40% by mass. The PC can was depressurized and 60 minutes later, a melt polymerization reaction was carried out at a final pressure of 0.5 hPa and a temperature of 275 ° C. for 4 hours to obtain a regenerated polyester resin (extreme viscosity: 0.64).

Comparative Example 6
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into the ES can, and then 7.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. When the internal temperature of the ES can stopped dropping, 55.0 parts by mass of recycled polyester was added in a fixed amount over a rotary valve for about 2 hours, and the contents solidified in the reactor, and the subsequent reaction continued. Became impossible.

Comparative Example 7
In the same manner as in Example 1, an ethylene terephthalate oligomer having an esterification reaction rate of 95% (number average degree of polymerization: 5) was obtained.
45.0 parts by mass of ethylene terephthalate oligomer was charged into an ES can, and then 7.0 parts by mass of ethylene glycol was added in a state where the stirrer of the ES can was rotated. From the place where the internal temperature drop of the ES can stopped, 55.0 parts by mass of recycled polyester raw material (similar to that in Example 1) was quantitatively charged over about 2 hours via a rotary valve. At this time, the recycled polyester raw material was added so that the G / A was 1.16. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 270 ° C. Then, the obtained depolymerized product was pressure-fed to the PC can by setting a candle filter with an opening of 20 μm between the ES can and the PC can, and then antimony trioxide was 1.0 × 10 ^{-4 as a polymerization catalyst.} Add mol / unit, cobalt acetate to 0.5 × 10 ^-4 mol / unit, and EG slurry of titanium dioxide to 0.40% by mass, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa. A melt polymerization reaction was carried out at a temperature of 255 ° C., but a regenerated polyester resin could not be obtained.

Test Example 1
The following characteristics were investigated for the recycled polyester resins obtained in Examples 1 to 9 and Comparative Examples 1 to 7, respectively. The results are shown in Table 1. The measurement or evaluation of each characteristic value was carried out as follows.

(A) Extreme Viscosity Using the obtained regenerated polyester resin, an equal mass mixture of phenol and ethane tetrachloride is used as a solvent, and the measurement is carried out at a temperature of 20 ° C.

(B) Composition of polyester resin The obtained polyester resin was dissolved in a mixed solvent having a volume ratio of deuterated hexafluoroisopropanol and deuterated chloroform of 1:20, and "LA-400 type NMR" manufactured by JEOL Ltd. 1H-NMR was measured with the apparatus, and the type and content of the copolymerization component were determined from the integrated intensity of the proton peaks of each component in the obtained chart.

(C) Concentration of carboxyl end groups 0.1 g of the obtained regenerated polyester resin was dissolved in 10 ml of benzyl alcohol, 10 ml of chloroform was added to this solution, and then titrated with a 1/10 specified potassium hydroxide benzyl alcohol solution. rice field.

(D) Average pressure boosting speed measured by a pressure tester Melt polyester resin at 300 ° C with an extruder, and use a stainless steel twill weave filter (nominal size mesh: 1400 mesh, weave) as a filter at the tip of the extruder. : Plain weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filter particle size: 12 μm, viscous resistance coefficient (m ^-1 ): 2.60 × 10 ^7, inertial resistance coefficient: 5.14 × 10, sets Co. Kamijo Seiki), further the back (downstream side) the reinforcing member (stainless steel plain weave wire mesh (nominal size mesh: 40 mesh, woven Method: Plain weave, Wire diameter: 0.21 mm (manufactured by Kamijo Seiki Co., Ltd.) After laminating, the polymer discharge rate is 29.0 g / min, and the filter pressure is increased. The measurement is performed using a detector. The pressure test using the above pressure tester is continuously performed for 12 hours, and the initial pressure value (MPa) at the time of starting the pressure test (5 to 10 after the polyester resin starts to pass through the filter). The minimum value of the pressure during the minute is the initial pressure.) And the final pressure value (MPa) after 12 hours have passed, the average boosting speed is calculated by the following formula.
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12

As is clear from the results in Table 1, the regenerated polyester resins obtained in Examples 1 to 9 have a carboxyl-terminal group amount, a diethylene glycol content, and an average step-up rate within the ranges specified in the present invention. Therefore, it was excellent in spinning operability.
On the other hand, in Comparative Example 1, since the G / A during the depolymerization reaction was low, the obtained regenerated polyester resin had a high carboxyl-terminal group concentration and a high average step-up rate.
In Comparative Example 2, since the G / A during the depolymerization reaction was high, the obtained regenerated polyester resin had a high content of diethylene glycol and a high average step-up rate.
In Comparative Example 3, since the depolymerization step was performed under heat treatment conditions at 290 ° C., the obtained regenerated polyester resin had a high carboxyl terminal group concentration and a high content of diethylene glycol.
In Comparative Example 4, since the filtration particle size of the candle filter provided between the ES can and the PC can was 30 μm, the obtained recycled polyester resin had a high average step-up rate.
In Comparative Example 5, since the production method of the present invention was not carried out and the G / A during the depolymerization reaction was high, the obtained regenerated polyester resin had a high content of diethylene glycol and a high average step-up rate. ..
In Comparative Example 6, since the depolymerization step was performed under heat treatment conditions at 230 ° C., the contents solidified in the reactor, and it became impossible to continue the reaction thereafter.
In Comparative Example 7, since the polycondensation reaction temperature in the polycondensation step was 255 ° C., the polymerization rate was slow and the regenerated polyester resin could not be obtained.

B. About fibers using recycled polyester resin
Example 10
The recycled polyester resin obtained in Example 1 is spun by an extruder type melt spinning machine from a spinning nozzle (hole diameter 0.15 mm, number of holes 84 holes) equipped with a filter having a resin temperature of 295 ° C. and a filtration particle size of 20 μm, and is 2900 m. It was wound at a spinning speed of / min. The obtained undrawn yarn was drawn with a drawing apparatus at a drawing temperature of 160 ° C. and a drawing ratio of 1.5 times to obtain a drawn multifilament yarn having a fineness of 35 dtex.

Example 11
Spinning and stretching were carried out in the same manner as in Example 10 except that the regenerated polyester resin obtained in Example 4 was used to obtain a drawn multifilament yarn.

Example 12
The recycled polyester resin obtained in Example 1 is spun by an extruder type melt spinning machine from a spinning nozzle (hole diameter 0.2 mm, number of holes 72 holes) equipped with a filter having a resin temperature of 301 ° C. and a filtration particle size of 15 μm, and is 3250 m. It was wound at a spinning speed of / min. The obtained undrawn yarn was drawn with a drawing apparatus at a drawing temperature of 160 ° C. and a drawing ratio of 1.6 times to obtain a drawn multifilament yarn having a fineness of 84 dtex.

Example 13
Spinning and stretching were carried out in the same manner as in Example 12 except that the regenerated polyester resin obtained in Example 4 was used to obtain a drawn multifilament yarn.

Comparative Example 8
An attempt was made to spin and draw in the same manner as in Example 10 except that the recycled polyester resin obtained in Comparative Example 1 was used. I couldn't.

Comparative Example 9
Spinning and stretching were carried out in the same manner as in Example 10 except that the regenerated polyester resin obtained in Comparative Example 2 was used to obtain a drawn multifilament yarn.

Test Example 2
The strength, elongation, number of fluffs, and operability (cutting yarn, pressurization) of the drawn multifilament yarns obtained in Examples 10 to 13 and Comparative Example 9 were examined. The results are shown in Table 2. The strength, elongation, number of fluffs, and operability (cutting yarn, pressurization) were measured or evaluated as follows.

(E) Strength and Elongation Measured based on JIS L1013 using Tencilon RTC-1210 (manufactured by Orientec).

With (f) fluff number drawn yarn was measured fluff number (pieces / 10 ⁸ m) with a warper. This measurement was performed with a fiber length of 3 × ¹⁰⁸ m.

(G) Operability (cutting thread, boosting)
Cutting yarn: The number of cutting yarns during continuous spinning for 24 hours was counted, and 3 times or less / 24 hours was designated as "◯", and 4 times or more / 24 hours was designated as "x".
Boosting: Spinning continuously for 24 hours, measuring the nozzle pack pressure during that time, "○" when the pressure is not increased by 2 MPa or more than the pressure set at the initial stage of spinning, and "○" when the pressure is increased as described above. It was set as "x".

As is clear from Table 2, in Examples 10 to 13, the multifilament yarn can be obtained with good spinning operability by using the recycled polyester resin, and the obtained multifilament yarn has good yarn physical characteristics. We were able to obtain fibers that did not cause any problems in practical use. In particular, in Examples 10 and 11, ultrafine multifilaments having a single fiber fineness of 0.5 decitex or less could be produced with good spinning operability.
On the other hand, in Comparative Example 8, since the regenerated polyester resin obtained in Comparative Example 1 was used, the pressure during spinning was intense and the number of cut yarns was high, so that undrawn yarn could not be obtained.
In Comparative Example 9, although the drawn multifilament yarn could be obtained, the yarn had low strength and low elongation, and fluff was frequently generated, which was problematic in practical use.

C. About molded products using recycled polyester resin
Example 14
The regenerated polyester resin (extreme viscosity 0.64) obtained in Example 1 was continuously supplied to a crystallizer, crystallized at 150 ° C., then supplied to a dryer and dried at 175 ° C. for 4 hours. After that, it is sent to a preheater, heated to 210 ° C., supplied to a solid phase polymerization machine, and a solid phase polymerization reaction is carried out at 210 ° C. for 30 hours in a nitrogen gas atmosphere to carry out a solid phase polymerization reaction at 210 ° C. for 30 hours. Got
The regenerated polyester resin obtained by the solid-state polymerization reaction is made into chips, dried, and then extruded at an extrusion temperature of 280 ° C. to form a cylindrical parison using a direct blow molding machine (manufactured by Tahara). While in the softened state, it was sandwiched between molds to form the bottom, which was blown to form a bottle. At this time, the bottom was formed when the parison diameter was 3 cm and the length was 25 cm, and blow molding was performed to obtain a 350 ml hollow container (direct blow molded product).

Example 15
A solid-phase polymerization reaction was carried out in the same manner as in Example 14 except that the regenerated polyester resin obtained in Example 4 was used to obtain a regenerated polyester resin having an ultimate viscosity of 1.15.
Using the regenerated polyester resin obtained by the solid-phase polymerization reaction, direct blow molding was performed in the same manner as in Example 14 to obtain a hollow container.

Comparative Example 10
A solid-phase polymerization reaction was carried out in the same manner as in Example 14 except that the regenerated polyester resin obtained in Comparative Example 1 was used to obtain a regenerated polyester resin having an ultimate viscosity of 1.18.
Using the regenerated polyester resin obtained by the solid-phase polymerization reaction, direct blow molding was performed in the same manner as in Example 14 to obtain a hollow container.

Comparative Example 11
A solid-phase polymerization reaction was carried out in the same manner as in Example 14 except that the regenerated polyester resin obtained in Comparative Example 2 was used to obtain a regenerated polyester resin having an ultimate viscosity of 1.20.
Using the regenerated polyester resin obtained by the solid-phase polymerization reaction, direct blow molding was performed in the same manner as in Example 14 to obtain a hollow container.

Test Example 3
Table 3 shows the evaluation results of the moldability, haze and impact resistance of the hollow containers obtained in Examples 14 to 15 and Comparative Examples 10 to 11. The moldability, haze and impact resistance were evaluated or measured as follows.

(H) Moldability The thickness of the body of the obtained container (100 samples) was measured, and the one with a thickness difference of up to 0.30 mm between the thickest part and the thinnest part was passed. The number of samples is shown.

(I) Haze A sample piece (20 pieces) was cut out from the obtained container, and the turbidity was measured with a turbidity meter MODEL 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (air: haze 0%), n number = The average value was 20. The smaller this value is, the better the transparency is, and if it is 6% or less, it is judged that the transparency is excellent.

(J) Impact resistance A molded product (100 samples) that passed the evaluation of moldability in (h) was filled with 340 ml of tap water, and 200 cm on a P tile at room temperature. From the height of the molded product, the molded product was dropped once with the bottom surface facing downward and the side surfaces facing downward. When the number of compacts that did not crack at this time was 90 or more, it was evaluated that the impact resistance was good.

As is clear from the results in Table 3, the hollow containers obtained in Examples 14 to 15 can be obtained with good moldability, and the obtained hollow containers have low haze, excellent transparency, and resistance. It was also excellent in impact resistance.
On the other hand, in Comparative Example 10, since a recycled polyester resin having a high carboxyl-terminal group concentration was used, the moldability was inferior, and the obtained hollow container was inferior in both transparency and impact resistance.
In Comparative Example 11, since a recycled polyester resin having a high content of diethylene glycol was used, the moldability was inferior, and the obtained hollow container was inferior in both transparency and impact resistance.

D. About film using recycled polyester resin
Example 16
A polyethylene terephthalate resin containing 93.5% by mass of the regenerated polyester resin (extreme viscosity 0.64) obtained in Example 1 and 1.5% by mass of silica particles was mixed as a master chip in an amount of 6.5% by mass. The resin is melt-kneaded in an extruder, supplied to a T-die, discharged into a sheet, wound around a metal drum temperature-controlled at 20 ° C, cooled and wound to produce an unstretched sheet with a thickness of about 150 μm. bottom. Next, the end of this unstretched sheet is held by a clip of a tenter type simultaneous biaxial stretching device, and under the condition of 180 ° C., the stretching ratio is 3.0 times in the MD direction and 3.3 times in the TD direction at the same time. After biaxial stretching, heat treatment was performed at 215 ° C. for 4 seconds with a relaxation rate of 5% in the TD direction, the mixture was slowly cooled to room temperature, and one side was subjected to a corona discharge treatment before winding. In this way, a biaxially stretched PET resin film having a thickness of 15 μm was obtained. The recycling ratio in this film was 51.4%.

Example 17
An unstretched sheet was produced in the same manner as in Example 16 except that the recycled polyester resin obtained in Example 4 was used instead of the recycled polyester resin obtained in Example 1, and the same as in Example 16. The film was stretched and heat-treated to obtain a biaxially stretched PET resin film having a thickness of 15 μm.

Comparative Example 12
An attempt was made to produce an unstretched sheet in the same manner as in Example 16 except that the recycled polyester resin obtained in Comparative Example 1 was used instead of the recycled polyester resin obtained in Example 1, but a T-die film was used. Due to the contamination of the lip surface, breakage of the film, roll contamination, etc., the production could not be performed within 2 hours from the start of operation, and the unstretched sheet could not be used in the stretching process to obtain a biaxially stretched PET resin film. I couldn't.

Comparative Example 13
An unstretched sheet was produced in the same manner as in Example 16 except that the recycled polyester resin obtained in Comparative Example 2 was used instead of the recycled polyester resin obtained in Example 1, and the same as in Example 16. The film was stretched and heat-treated to obtain a biaxially stretched PET resin film having a thickness of 12 μm. However, for the same reason as in Comparative Example 12, continuous operation could not be performed for 24 hours or more, and production could not be performed in 14 hours.

Test Example 4
Table 4 shows the characteristic values and operability evaluation results of the biaxially stretched PET resin films obtained in Examples 16 to 17 and Comparative Example 13. The tensile strength, haze and operability were evaluated or measured as follows.

(K) Tensile strength (MPa)
The tensile strength was measured according to JIS K7127 using a DSS-500 type autograph manufactured by Shimadzu Corporation. The central portion of the biaxially stretched PET resin film obtained in Examples and Comparative Examples in the TD direction was cut out to a width of 10 mm and a length of 150 mm in the MD direction and the TD direction, respectively, as a sample. The measurement was carried out under the conditions of a measurement length of 100 mm and a tensile speed of 500 mm / min, and the measurement was performed by the following formula.
Tensile strength (MPa) = tensile load at break (N) / original average cross-sectional area of the measurement sample (mm ² )

(L) Haze (%)
Using a haze meter (NDH4000) manufactured by Nippon Denshoku Co., Ltd., the central portion of the biaxially stretched PET resin film obtained in each Example and Comparative Example was measured in the TD direction according to JIS K7136.

(M) Operability
In the situation where the polyester film was continuously produced, it was evaluated according to the following criteria.
◯: It was possible to operate continuously for 24 hours or more.
X: During continuous operation for 24 hours, the film could not be produced due to contamination of the lip surface of the T-die, film breakage, roll contamination, and the like.

As is clear from the results in Table 4, the biaxially stretched PET resin films obtained in Examples 16 to 17 have high tensile strength in both MD and TD directions, low haze, excellent transparency, and virginity. It had characteristics comparable to those of a film made of polyester resin. Furthermore, these were also good in operability.
On the other hand, in Comparative Example 12, since a recycled polyester resin having a high carboxyl-terminal group concentration and a high average step-up rate was used, the operability was inferior and a biaxially stretched PET resin film could not be obtained.
In Comparative Example 13, since a recycled polyester resin having a high content of diethylene glycol was used, the operability was inferior, and the obtained biaxially stretched PET resin film was inferior in both tensile strength and transparency.

Claims (6)

A polyester resin containing components derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resins generated in the process of manufacturing polyester products.
(1) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less.
(2) The carboxyl terminal group concentration is 30 equivalents / t or less, and
(3) The average boosting speed is 0.6 MPa / h or less (however, the average boosting speed is a value calculated by the following procedure: using a boosting tester including an extruder and a pressure sensor, the extruder Stainless steel filter at the tip (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size : 12 μm) is set, the polyester resin is melted at 300 ° C. with an extruder, and the extruding is started as the pressure value applied to the filter when the melt is extruded at a discharge rate of 29.0 g / min from the filter. If the pressure value at that time is the "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is the "final pressure value (MPa)", the following calculation is performed based on those pressure values. The above average boosting speed is calculated by the formula A:
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12) ... A),
Recycled polyester resin characterized by this. A fiber containing the recycled polyester resin according to claim 1. A blow-molded product containing the recycled polyester resin according to claim 1. A film containing the recycled polyester resin according to claim 1. A method for producing a recycled polyester resin using at least one recycled polyester raw material of unadopted polyester generated in the process of producing a used polyester product and b) a polyester product.
(1) The raw material is added to a mixture containing an ethylene terephthalate oligomer and ethylene glycol so that the molar ratio of the total glycol component / total acid component is 1.08 to 1.35, and heat treatment is performed at 245 to 280 ° C. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under conditions,
(2) A step of collecting the filtrate by passing the reaction product through a filter having a filtration particle size of 10 to 25 μm.
(3) A method for producing a regenerated polyester resin, which comprises a step of adding a polymerization catalyst to the filtrate and carrying out a polycondensation reaction of the depolymerized product under a reduced pressure of 260 ° C. or higher and 1.0 hPa or lower. The production method according to claim 5, wherein the raw material contains at least 40% by mass or more of a) a used polyester product and b) at least one of unadopted polyester resins generated in the process of producing the polyester product.