JP2023027592A - Recycled polyester resin and method for producing recycled polyester resin - Google Patents

Abstract

To provide a recycled polyester resin which has a usage ratio of a recycled polyester raw material of 80% or more, and can be used for production of polyester products of various forms.SOLUTION: A polyester resin contains a) a used polyester product, and b) 80 mass% or more of a component derived from at least one recycled polyester raw material of an unemployed polyester resin generated in a process of producing a polyester product, wherein (1) when the total amount of the total glycol component is 100 mol%, a content of diethylene glycol is 4 mol% or less, (2) carboxyl terminal group concentration is 40 eq./t or less, and (3) average pressure increasing speed is 0.6 MPa/h or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a novel recycled polyester resin and a method for producing a recycled polyester resin. In particular, the present invention contains 80% by mass or more of components derived from recycled polyester raw materials including unused polyester resins generated in the process of manufacturing used polyester products and polyester products, has a small amount of foreign matter mixed in, and is a virgin polyester resin. It relates to a recycled polyester resin that can be processed into various molded products in the same manner as and a method for producing the same.

Polyethylene terephthalate (hereinafter sometimes abbreviated as PET) has a high melting point, chemical resistance, and is relatively inexpensive, so it is widely used for molded articles such as fibers, films, and PET bottles.
These polyester products inevitably generate scraps during the manufacturing and processing stages, and are often disposed of after use. is short. On the other hand, if it is not incinerated, it will remain semi-permanently because it will not rot and decompose.
In recent years, plastic containers discarded as garbage have flowed into the ocean via rivers, and microplastics that have been finely crushed by the action of waves and tidal currents accumulate in the bodies of marine organisms and accumulate in the food chain, contributing to the ecology of marine organisms. The fact that plastics have an adverse effect on systems and that plastics are a major cause of marine pollution have been viewed as problems, and there is a worldwide movement to reduce the amount of plastics used and switch to biodegradable plastics.

From the viewpoint of reducing the amount of such plastic products used and from the viewpoint of environmental problems, various recycling methods for reusing resources have been carried out. As for polyester products, a method of recycling polyester waste generated in the manufacturing process and a method of recovering and reusing as a raw material a product that has been discarded once on the market is being studied.
Especially in recent years, with regard to textile products, eco-marked products that are certified by achieving a certain recycling rate have become widespread.

Various methods have been proposed for recycling recycled polyester raw materials. For example, a method of adding methanol to PET waste to decompose 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); A method (Patent Document 3) and the like have been proposed.

In addition, problems that arise when recycling PET bottles that have once been made into products include additives added to the polyester resin, and caps (aluminum, polypropylene, polyethylene) and inner plugs attached to the bottle body. and liners (polypropylene, polyethylene), labels (paper, polystyrene and other resins, inks), adhesives, printing inks, etc.
As a pretreatment for the recycling process, first, collected PET bottles are passed through a vibrating sieve to remove sand, metals, and the like. After that, the PET bottles are washed, the colored bottles are separated, and then coarsely pulverized. Labels and the like are then removed by air separation. Further, the pieces of PET bottles are finely pulverized, except for the pieces of aluminum derived from the cap and the like. Components such as adhesives, proteins and molds are removed by high-temperature alkaline washing, and different components such as polypropylene and polyethylene are separated by specific gravity.

However, even through these steps, it was particularly difficult to completely separate non-polyester resins such as polypropylene, polyethylene and polystyrene as described above. Therefore, even if the recycled polyester resin is obtained by the recycling method described in Patent Documents 1 to 3 as described above, the foreign matter derived from the non-polyester resin cannot be sufficiently removed, and the amount of foreign matter mixed in cannot be sufficiently reduced. However, it was not possible to obtain a product having the same quality as the virgin polyester resin. Moreover, the methods of Patent Documents 1 to 3 require a large amount of cost for installation, operation, maintenance, etc. of the recovery apparatus, and there is room for improvement in terms of practicality.

Further, the invention described in Patent Document 4 describes a method in which polyester waste is depolymerized with ethylene glycol, filtered through a filter having an average mesh size of 10 to 50 μm, and then subjected to a repolymerization reaction. It is also shown that the resulting recycled polyester resin has a small amount of foreign matter mixed in and is excellent in workability during processing. However, even in this method, the above-described non-polyester resin-derived foreign matter cannot be sufficiently removed, and the amount of foreign matter mixed in cannot be sufficiently reduced.

In particular, when a polyester resin is melt-spun to produce fibers, the amount of foreign matter mixed in has a great effect on productivity. When manufacturing fibers, in the melt spinning process, resin is extruded from a nozzle with a small hole diameter, a large number of extruded filamentous materials are taken up by a roller, subjected to drawing and heat treatment as necessary, and further a winding process. pass. In this case, if a resin mixed with foreign matter is used, troubles such as yarn breakage are likely to occur in any of the melt spinning, drawing/heat treatment, and winding processes, making it difficult to carry out stable production. This problem becomes even more pronounced when attempting to produce finer fibers.

Furthermore, due to the growing awareness of environmental issues, there is a growing demand for recycled polyester resins that use a high percentage of recycled raw materials. Recycled polyester resins with a recycled raw material usage rate of 80% or more, and further with a recycled raw material usage rate of 100%, have a remarkable problem of contamination with foreign matter as described above, and are also inferior in thermal stability. As a matter of course, it has been more difficult to obtain fine fibers by melt spinning.

Therefore, the main object of the present invention is to solve the above problems, and to obtain at least one recycled polyester raw material from a) used polyester products and b) unadopted polyester resin generated in the process of manufacturing polyester products. It is an object of the present invention to provide a recycled polyester resin containing 80% by mass or more of a component that can be used for the production of various types of polyester products.

Japanese Patent Publication No. 42-8855 JP-A-48-62732 JP-A-60-248646 JP 2005-171138 A

To solve the above problems, the present invention uses at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resin generated in the process of manufacturing polyester products, and these recycled polyesters An object of the present invention is to provide a recycled polyester resin having a content of components derived from raw materials of 80% by mass or more and which can be used in the production of various forms of polyester products. Another object of the present invention is to provide a production method capable of obtaining such a recycled polyester resin of the present invention.

As a result of extensive research in view of the problems of the conventional technology, the present inventors have found that by adopting a specific manufacturing method using recycled polyester raw materials, the amount of foreign matter mixed in is as small as that of virgin polyester resin. The inventors have also found that a recycled polyester resin having excellent thermal stability can be obtained, and have completed the present invention.

That is, the gist of the present invention is the following (a) to (e).

(a) A polyester resin containing 80% by mass or more of at least one component derived from recycled polyester raw materials of a) used polyester products and b) unused polyester resin generated in the process of manufacturing polyester products, A recycled polyester resin characterized by satisfying all of the following (1) to (3).
(1) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less,
(2) a carboxyl terminal group concentration of 40 equivalents/t or less;
(3) The average pressurization rate is 0.6 MPa / h or less (however, the average pressurization rate is a value calculated by the following procedure: Using a pressurization tester including an extruder and a pressure sensor, the extruder Stainless steel filter at the tip (nominal size mesh: 1400 mesh, weaving method: twilled dutch, 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 pressure value applied to the filter when extruding the melt at a discharge rate of 29.0 g / min from the filter is the start of extrusion. If the pressure value at the time of extrusion is defined as "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is defined as "final pressure value (MPa)", the following calculation is based on those pressure values. Calculate the average pressure rise rate by Equation A:
Average pressure increase rate (MPa/h) = (final pressure value - initial pressure value) / 12) ... A)
(b) A molded article containing the recycled polyester resin described in (a).
(c) A fiber containing the recycled polyester resin described in (b).
(d) A film containing the recycled polyester resin described in (a).
(e) A method for producing a recycled polyester resin using at least one recycled polyester raw material from among a) used polyester products and b) unused polyester resin generated in the process of producing polyester products, the method comprising the following (1 ) to (4) are all included.
(1) Ethylene glycol is added to the raw material so that the total glycol component/total acid component molar ratio is 1.04 to 1.40, and depolymerization is performed under heat treatment conditions of 220 to 285°C. , a step of obtaining a depolymer having a melt viscosity of 10 to 1500 mPa s (2) A step of passing the depolymer through a filter having a filtration particle size of 10 to 25 μm to recover a filtrate (3) Adding a polycondensation catalyst to the filtrate (4) a step of subjecting the reaction product to a polycondensation reaction at a temperature of 260° C. or higher and under reduced pressure of 1.0 hPa or lower

The recycled polyester resin of the present invention contains 80% by mass or more of a component 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. Also, the content of carboxyl terminal groups and the content of diethylene glycol satisfies specific ranges, and the amount of contamination with foreign matter is small, and the thermal stability is excellent. For this reason, for example, in the process of obtaining fibers by melt spinning, the process of obtaining sheets or films by film formation, and the process of obtaining moldings such as bottles, continuous operation over a relatively long period of time is possible, and products of various forms can be produced with high productivity. can be manufactured.

In addition, according to the method for producing the recycled polyester resin of the present invention, it is possible to obtain the recycled polyester resin of the present invention at low cost with good operability without the need for complicated processes or equipment, which has practical merits. It is big.

The present invention will be described in detail below.
The recycled polyester resin of the present invention (hereinafter sometimes referred to as the resin of the present invention) is at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resin generated in the process of manufacturing polyester products. It is a polyester resin containing 80% by mass or more of a component derived from.

Examples of the used polyester products of a) above include, for example, polyester molded articles (including fibers) that have been put on the market once and collected after use. Typical examples include containers or packaging materials such as PET bottles.
Unused polyester resin generated in the process of manufacturing polyester products in b) above is polyester that has not been commercialized. Fragments, scraps generated during molding, processing, etc., cuttings of transitional products generated at the time of brand change, cuttings of prototypes and defective products, etc.

The above a) and b) are not limited in their form, etc., and may be pelletized by further processing such as pulverization and cutting as necessary, or may be melted and pelletized. good.
The above a) and b) may be used alone or in combination.
In addition, the recycled polyester raw materials of a) and b) may be either crystalline or amorphous. Therefore, for example, pellets of amorphous polyester waste not subjected to heat treatment, crystalline pellets subjected to heat treatment, mixtures of crystalline pellets and amorphous pellets, and the like can be used. In the present invention, it is preferable to use a crystalline recycled polyester raw material for the purpose of preventing fusion between pellets, particularly during charging into a can or depolymerization reaction. Therefore, it is possible to preferably use a material obtained by crystallizing the above material a) or b) by heat treatment (crystallized pellets, etc.).

In addition, the properties of the recycled polyester raw materials of a) and b) are not limited, and may be in the form of a) and b), or cut pieces obtained by further processing such as cutting and crushing. , pulverized products (powder) and the like, as well as solid forms such as compacts (such as pellets) formed by molding these. More specific examples include pellets obtained by cooling and cutting melted polyester scraps, cut pieces obtained by finely cutting polyester molded articles such as PET bottles, and the like. In addition, it may be in the form of a liquid obtained by dispersing or dissolving the above cut pieces, pulverized material (powder), etc. in a solvent. When these raw materials are used to produce polyester products, they can be melted at a temperature higher than their melting point and put into a can as a melt, if necessary.

Since the object of the present invention is to obtain a recycled polyester resin with a high usage rate of recycled polyester raw materials, the recycled polyester resin of the present invention is derived from at least one of the above a) and b) recycled polyester raw materials. It contains 80% by mass or more of the component, preferably 85% by mass or more. The recycled polyester resin of the present invention can be obtained by the production method of the present invention, which will be described later, but it is also possible to easily obtain a recycled polyester resin containing 100% of the components derived from recycled polyester raw materials, that is, composed only of recycled raw materials. is possible.

When the total amount of all glycol components in the resin of the present invention is 100 mol %, ethylene glycol accounts for 80 mol % or more of the total glycol components, preferably 85 mol % or more. If the ethylene glycol content is less than 80 mol %, the obtained polyester resin tends to be inferior in crystallinity and heat resistance.

In the resin of the present invention, the content of diethylene glycol is 4 mol % or less, preferably 3.5 mol % or less, when the total amount of all glycol components is 100 mol %. 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 raw materials, and diethylene glycol may be produced as a by-product at that time. The resin of the present invention contains a small amount of diethylene glycol 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 becomes possible to obtain molded articles such as fibers, injection molded articles, various blow molded articles, sheets, films, etc. with good productivity. The lower limit of the diethylene glycol content can be, for example, about 0.5 mol %, but is not limited to this.

Further, the resin of the present invention preferably contains terephthalic acid in an amount of 80 mol % or more when the total amount of all acid components constituting the polyester is 100 mol %. That is, terephthalic acid is the main component as the acid component. The proportion of terephthalic acid in the acid component is 80 mol % or more, and the proportion of terephthalic acid is preferably 90 mol %. If the proportion of terephthalic acid is less than 80 mol %, the crystallinity of the resin composition tends to be lowered and the resin composition tends to become amorphous, which is not preferable.

Diol components other than ethylene glycol and diethylene glycol among all the glycol components in the resin of the present invention include, for example, cyclohexanedimethanol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, dimer diol, ethylene oxide adduct of bisphenol S, ethylene oxide adduct of bisphenol A, and the like can be used.

Acid components other than terephthalic acid in the resin of the present invention include isophthalic acid, phthalic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, adipic acid, sebacic acid, dimer acid, and the like. Two or more types may be used in combination, and ester-forming derivatives of these acids may also be used.

As for the resin of the present invention, polyethylene terephthalate, which is a polycondensation product of ethylene glycol and terephthalic acid, can be obtained in the production method of the recycled polyester resin of the present invention, which will be described later. When other components are present, a polyester resin copolymerized with these components may be produced by a polycondensation reaction. For this reason, the recycled polyester resin may be copolymerized with the above-mentioned components as an acid component or a glycol component, in addition to polyethylene terephthalate, which is the main component. Two or more of these components may be contained.

The resin of the present invention contains a polycondensation catalyst, and may contain various additives depending on the application.
First, as the polycondensation catalyst, at least one of germanium compounds, antimony compounds, titanium compounds, cobalt compounds, zinc compounds, tin compounds and the like can be used, although not limited thereto. Among them, it is particularly preferable to use at least one of a germanium compound and an antimony compound. When the transparency of the resulting recycled polyester resin is important, it is preferable to use a germanium compound. As the above compounds, oxides such as germanium, antimony, titanium and cobalt, inorganic acid salts, organic acid salts, halides and sulfides can be used.

The amount of the polycondensation catalyst to be used is not particularly limited, but for example, it is preferably 1×10 ⁻⁵ mol or more, preferably 6×10 ⁻⁵ mol or more, per 1 mol of the acid component of the polyester resin to be produced. is more preferable. The upper limit of the amount used can be, for example, about 1×10 ⁻³ mol, but is not limited to this.

The polycondensation catalyst contained in the recycled polyester raw material may also act as a catalyst during the polycondensation reaction, so when adding the polycondensation catalyst in the polycondensation process, the polycondensation catalyst contained in the recycled polyester raw material It is preferable to consider the type of catalyst and its content.

Various additives added depending on the application include fatty acid esters that can adjust the melt viscosity, hindered phenolic antioxidants, phosphorus compounds that can suppress thermal decomposition of the resin, and improve the appearance of the resin. and a titanium compound that improves the whiteness of the resin, a crystal nucleating agent that improves the crystallinity of the resin, and the like.

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

Examples of hindered phenol antioxidants include 2,6-di-t-butyl-4-methylphenol, 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 preferred from the viewpoint of effect and cost. These can be used alone or in combination of two or more.

Phosphorus compounds such as phosphorous acid, phosphoric acid, trimethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, triethyl phosphate, tridecyl phosphate, and triphenyl phosphate are used as the phosphorus compound. be able to. These can be used alone or in combination of two or more.

Examples of color tone modifiers include cobalt compounds such as cobalt acetate, manganese compounds such as manganese acetate, dyes (blue, purple, and red), and copper phthalocyanine compounds. Among them, cobalt acetate and dyes are preferable from the viewpoint of polycondensation catalytic activity, physical properties of the resulting polyester resin, and cost.
In addition, it is preferable that the dye contains a blue dye, a red dye, a purple dye, or the like, because the color tone is good.

In addition, as dyes, blue dyes such as SOLVENT BLUE 104, SOLVENT BLUE 122, and SOLVENT BLUE 45, SOLVENT RED 111, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, P IGMENT RED 263, red dyes such as VATRED 41; and purple dyes such as DESPERSE VIOLET 26, SOLVENT VIOLET 13, SOLVENT VIOLET 37, and SOLVENT VIOLET 49. Among them, SOLVENT BLUE 104, SOLVENT BLUE 45, SOLVENT RED 179, SOLVENT RED 195, SOLVENT RED 135, and SOLVENT which do not contain halogen, which tends to cause equipment corrosion, have relatively good heat resistance at high temperatures, and have excellent color development. VIOLET 49 is preferred. These can be used alone or in combination of two or more.

Titanium oxide is preferably used as the titanium compound. Titanium oxide is generally used as a matting agent or white pigment for polyester resins. By adding an appropriate amount of titanium oxide to the resin of the present invention, the whiteness of the fiber is improved, It is preferable in that a woven or knitted fabric with a good color tone can be obtained. The amount of titanium oxide to be added is preferably 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyester resin.

Crystal nucleating agents include carbon black, calcium carbonate, synthetic silicic acid and silicates, zinc oxide, high-site clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, and titanium oxide. , zinc oxide, antimony oxide, barium sulfate, calcium sulfate, alumina, calcium silicate, boron nitride, etc.; compounds and the like. Among them, mica, talc, and high molecular weight organic compounds are preferred. These can be used alone or in combination of two or more.

The resin of the present invention has the composition as described above and the characteristic values shown below.
(a) a carboxyl terminal group concentration of 40 equivalents/t or less (b) an average pressurization rate of 0.6 MPa/h or less measured by a pressurization tester It can be obtained by a manufacturing method.

First, as the characteristic value of (a), the resin of the present invention has a carboxyl terminal group concentration of 40 equivalents/t or less, preferably 30 equivalents/t or less, and more preferably 25 equivalents/t or less. preferable.
Since the resin of the present invention has a carboxyl terminal group concentration of 40 equivalents/t or less, it has excellent performance in terms of thermal stability, and it is possible to obtain various molded products with high productivity by various molding methods. becomes.

Although the intrinsic viscosity of the recycled polyester resin of the present invention is not particularly limited, it is usually preferably about 0.44 to 0.80. Further, as described later, the recycled polyester resin of the present invention can be used for molding by increasing the degree of polymerization through a solid phase polymerization process. In this case, the intrinsic viscosity of the resulting recycled polyester resin is preferably 0.80 to 1.25. In addition, the intrinsic viscosity (IV) is measured at a temperature of 20° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.

As the characteristic value of (b), the resin of the present invention has an average pressure increase rate measured by the following method of 0.6 MPa/h or less, preferably 0.5 MPa/h or less, especially 0.4 MPa/h. The following are preferable. The average pressurization rate in the present invention is an index of the amount of foreign substances derived from various inorganic substances and foreign substances derived from non-polyester resins. is shown. The lower limit of the average pressure increase rate can be set to, for example, about 0.01 MPa/h, but is not limited to this.

The method for measuring the average pressurization rate uses a pressurization tester including an extruder and a pressure sensor, and a stainless steel filter (nominal size mesh: 1400 mesh, weave: twill weave, vertical mesh: 165 mesh) at the tip of the extruder , horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration particle size: 12 μm), the polyester resin is melted at 300 ° C. in an extruder, and the discharge amount from the filter As the pressure value applied to the filter when the melt is extruded at 29.0 g / min, the pressure value at the start of extrusion is defined as the “initial pressure value (MPa)”, and the pressure value at the time of continuous extrusion for 12 hours. When the pressure value is the "final pressure value (MPa)", the average pressure increase rate is calculated by the following formula A based on those pressure values.
Average pressure increase rate (MPa/h) = (final pressure value - initial pressure value) / 12) ... A)

By adopting the production method described later, the resin of the present invention can reduce the amount of foreign substances derived from various inorganic substances and foreign substances derived from non-polyester resins. It is possible to reduce the average pressure rise rate measured by a tester to 0.6 MPa/h or less.

As the extruder, filter and the like used in the above measurements, known or commercially available ones can be used as appropriate as long as they satisfy the stipulations of the present invention.

In the present invention, if necessary, a reinforcing material may be added to the filter within a range that does not substantially affect the measurement results, as shown in the examples below. In the above measurement method, extremely high pressure is applied to the filter, so the filter alone may be deformed or damaged. In such cases, it is preferable to support the filter with stiffeners. A mesh-like metal member or the like can be used as the reinforcing material. More specifically, a metal filter having a strength that prevents deformation of the filter and having a coarse mesh that does not substantially affect the measurement results can be suitably used as the reinforcing material. Then, such a reinforcing material can be used by laminating it on the downstream side of the filter.

Next, a method for producing the resin of the present invention will be described. In the production method of the present invention, it is important to perform the steps (1) to (4) in order.
(1) Ethylene glycol is added to the raw material so that the total glycol component/total acid component molar ratio is 1.04 to 1.40, and depolymerization is performed under heat treatment conditions of 220 to 285°C. (2) passing the depolymer through a filter having a filtration particle size of 10 to 25 μm to collect a filtrate (3) adding a polycondensation catalyst to the filtrate; and kneading to obtain a reaction product;

First, in the depolymerization step (1), ethylene glycol is added to the recycled polyester raw material so that the molar ratio of all glycol components/total acid components is 1.04 to 1.40, and heat treatment is performed at 220 to 285 ° C. By carrying out depolymerization under these conditions, a depolymer having a melt viscosity of 10 to 1500 mPa·s is obtained.
In the production method of the present invention, the melt viscosity of the depolymer is a value measured at the heat treatment temperature during depolymerization, and is measured using a VISCO METER DV2T type melt viscometer manufactured by Brookfield.

Ethylene glycol added to the recycled polyester raw material can be obtained by a known method or commercially available.

In the step (1), when the ethylene glycol and the recycled polyester raw material are added, the total glycol component/total acid component molar ratio is 1.04 to 1.40 while stirring, and the molar ratio is 220 to 285. C. to obtain a depolymer having a melt viscosity of 10 to 1500 mPa.s.
This step is important in the production method of the present invention. That is, in the present invention, the recycled polyester raw material is depolymerized in the presence of ethylene glycol. Ethylene glycol and recycled polyester raw materials are added so as to have a pH of 1.04 to 1.40, and depolymerization is carried out.

The input amount (addition amount) of the recycled polyester raw material is preferably 65 parts by mass or more when the total input amount is 100 parts by mass, especially 70 parts by mass or more, and more preferably 80 parts by mass or more. Preferably, it is 85 parts by mass or more, most preferably. The amount of ethylene glycol added is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, when the total amount is 100 parts by mass.
If the amount of ethylene glycol to be added is less than the above range, blocking between the recycled polyester raw materials tends to occur when the recycled polyester raw materials are added, which is not preferable because the stirrer is subjected to an excessive load.

In addition, when the content of the component derived from the recycled polyester raw material in the recycled polyester resin obtained by the production method of the present invention is less than 100% by mass and is 80% by mass or more, in the step (1), ethylene In addition to the glycol and recycled polyester raw material, ethylene terephthalate oligomers may be added for depolymerization. Also when the ethylene terephthalate oligomer is added, it is necessary to adjust the molar ratio of all glycol components/total acid components to 1.04 to 1.40.

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

In step (1), it is important to set the melt viscosity of the depolymer obtained by performing the above depolymerization to 10 to 1500 mPa·s.
By performing depolymerization by adjusting the molar ratio of all glycol components / all acid components and obtaining a depolymer with a melt viscosity of 10 to 1500 mPa s, not only various inorganic substances contained in recycled polyester raw materials, but also non- Since foreign substances derived from the polyester resin are deposited efficiently, these foreign substances can be completely filtered in the step (2).

Then, in the step (3) of adding and kneading the polycondensation catalyst and various additives added according to the application, it is possible to uniformly knead without aggregating the polycondensation catalyst and various additives. .
As a result, in the polycondensation reaction of the step (4), the characteristic values of the present invention are that the diethylene glycol content (copolymerization amount) and the carboxyl terminal group concentration are not more than a specific amount, and the amount of foreign matter mixed in. It is possible to obtain a recycled polyester resin with less

In the step (1) of the present invention, it is desirable that the depolymerization reaction described above decomposes the recycled polyester raw material into oligomers having about 5 to 20 repeating units without decomposing them into monomers.

If the molar ratio of the total glycol component/total acid component during the depolymerization reaction is outside the above range, the resulting recycled polyester resin will have at least one of the carboxyl terminal group concentration and the diethylene glycol content specified in the present invention. is not satisfied, and the average boosting speed is high. This is because, when the molar ratio of all glycol components/total acid components during the depolymerization reaction is outside the above range, precipitation of various inorganic substances in the recycled polyester raw material and foreign matters derived from non-polyester resins is efficiently carried out. Therefore, in the step (2), these foreign substances cannot be completely filtered out, and the foreign substances precipitate after the polycondensation reaction in the step (4), resulting in a recycled polyester resin with a high average pressurization rate. .

In addition, in the defusion reaction step (1), if the melt viscosity of the resulting depolymer is less than 10 mPa·s, the viscosity becomes too low, and liquid leakage occurs from the pipe and the filter connection portion during filtering of foreign matter. It is easy to filter, the filtration efficiency is poor, foreign matter cannot be filtered sufficiently, and productivity deteriorates. On the other hand, if the melt viscosity of the depolymer exceeds 1500 mPa s, the viscosity becomes too high, which increases the load on the stirring blade during the depolymerization reaction, and also increases the pressure when filtering foreign matter, resulting in production. sexuality worsens.

In the production method of the present invention, the reactor used in the step (1) has no particular problem with the capacity and shape of the stirring blades of a commonly used esterification reactor. In order to proceed, it is preferable to have a structure in which a distillation column is provided side by side so as not to distill ethylene glycol out of the system.
When the recycled polyester raw material is added, it is preferably stirred under normal pressure, and more preferably after purging with a small amount of inert gas (generally nitrogen gas is used).

In addition, when performing a depolymerization reaction using an ester reactor, a method of performing the depolymerization reaction by adding the recycled polyester raw material and ethylene glycol in multiple times, or a method of adding the recycled polyester raw material to the ethylene glycol. It is preferable to employ a method of adding little by little.

When performing the depolymerization reaction, a melt extruder may be used instead of the ester reactor. In the method using a melt extruder, the polymer is sealed in the extruder and extruded, so there is no contact with air (especially oxygen), so there is no oxidative decomposition of the polymer, resulting in color deterioration and an increase in carboxyl end groups. The problem of viscosity reduction of the molten polymer associated with this does not occur. Moreover, if a melt extruder is used, the reaction can be carried out under all pressure conditions such as normal pressure, increased pressure, and reduced pressure.
The melt extruder may be either a single-screw extruder or a twin-screw extruder, but it is preferable to use a twin-screw extruder because the above advantages can be easily obtained.

Furthermore, when using a melt extruder in step (1), the depolymerization reaction proceeds inside the extruder by supplying ethylene glycol to the inside of the extruder. When supplying the recycled polyester raw material, adding ethylene glycol and passing it through a melt extruder makes it easier to lower the viscosity, and discharge from the tip nozzle becomes smooth. Also, the melting temperature of the melt extruder (the temperature of the depolymerization reaction) can be lowered by changing the pressure conditions to lower the viscosity.

The melt viscosity of the depolymerized product can be adjusted within the range of the present invention by appropriately adjusting the molar ratio of all glycol components/total acid components, heat treatment temperature, heat treatment time, pressure, etc. during depolymerization. Become.

The reaction temperature during the depolymerization performed in step (1) is preferably carried out by setting the internal temperature of the reactor or melt extruder in the range of 220 to 285 ° C., especially the internal temperature in the range of 245 to 280 ° C. is more preferable. If the reaction temperature during depolymerization is less than 220°C, a long heat treatment is required to reduce the melt viscosity of the depolymerized product to 1500 mPa s or less, resulting in poor workability and the resulting recycled polyester resin. , the color tone deteriorates, and the content of diethylene glycol and the concentration of carboxyl terminal groups increase.
On the other hand, when the reaction temperature exceeds 285° C., the melt viscosity of the depolymerized product becomes too low, and the diethylene glycol content and carboxyl terminal group concentration of the resulting recycled polyester resin become high.
The reaction time at the time of depolymerization (reaction time after the completion of the addition of the recycled polyester raw material) is preferably within 4 hours, and within 2 hours from the viewpoint of suppressing the amount of by-product diethylene glycol and suppressing the deterioration of the color tone of the polyester. is more preferable.

In the step (2), the depolymerized product obtained by the depolymerization reaction in the step (1) is passed through a filter having a filtration particle size of 10 to 25 μm to filter out foreign matters. As described above, by performing a depolymerization reaction under the conditions of the step (1) and obtaining a depolymer having a melt viscosity within a specific range, even if the amount of recycled polyester raw material used is large, these raw materials Not only various inorganic substances abundantly contained in the resin, but also foreign substances derived from non-polyester resins are deposited efficiently. Therefore, by passing through a filter having a filtration particle size of 10 to 25 μm, the precipitated foreign matter can be completely caught by the filter, and a filtrate containing a small amount of foreign matter can be obtained.
If a filter with a filtration particle size of more than 25 μm is used, foreign matter in the depolymerized product cannot be sufficiently removed, and the resulting regenerated polyester resin contains a large amount of foreign matter. For this reason, when spinning is performed using such a resin, pressure rise in the nozzle pack and yarn breakage occur. On the other hand, when a filter having a filtration particle size of less 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 also deteriorates operability.

In addition, as the filter that can be used in the step (2) of the production method of the present invention, there is no particular problem with general filters, but examples thereof include screen changer filters, leaf disk filters, candle-type sintered filters, and the like.

Then, in step (3) of the production method of the present invention, the polycondensation catalyst as described above is added to the filtrate obtained through step (2) above, and the mixture is kneaded to obtain a reaction product. In the step (3), it is preferable to add additives according to various uses together with the polycondensation catalyst and knead the mixture. In addition, the above-mentioned additive can be used for the additive added according to various uses.
The temperature at which kneading is performed in step (3) is preferably within the range of plus or minus 10° C. of the temperature at which polycondensation reaction is performed in step (4).

Next, as the step (4), the reaction product obtained in the step (3) is subjected to a polycondensation reaction in a polycondensation reactor at a temperature of 260° C. or higher and a reduced pressure of 1.0 hPa or lower.
If the polycondensation reaction temperature is less than 260° C. or the pressure during the polycondensation reaction exceeds 1.0 hPa, the polycondensation reaction time will be long, resulting in poor productivity or slow progress of the polycondensation reaction. , the recycled polyester resin cannot be obtained.
More preferably, the polycondensation reaction temperature is 270° C. or higher. However, if the polycondensation reaction temperature is too high, the polymer will be colored due to thermal decomposition, and the color tone will deteriorate, and the amount of terminal groups (COOH) will increase due to thermal decomposition. , 285° C. or lower. The intrinsic viscosity of the recycled polyester resin (prepolymer) obtained here is preferably 0.44 to 0.80.

Furthermore, in order to increase the intrinsic viscosity of the recycled polyester resin, it is preferable to subject the prepolymer obtained by the polycondensation reaction to solid phase polymerization. At this time, the prepolymer is made into chips of any shape such as dice or cylinder, and the polyester chips are continuously supplied to a crystallizer and crystallized at a temperature of 150 to 190° C., and then placed in a dryer. After drying at a temperature of 190° C. or less for 4 to 16 hours, it is sent to a preheater and heated to the following solid phase polymerization temperature for 2 to 5 hours, and then continuously fed to a solid phase polymerizer. A polyester resin having a target intrinsic viscosity can be obtained by performing a solid phase polymerization reaction. Solid state polymerization is preferably carried out under an inert gas such as nitrogen gas. Solid phase polymerization is usually carried out at a temperature within the range of 170 to 230°C, more preferably within the range of 180 to 220°C. Moreover, the polymerization time is in the range of 20 hours to 80 hours, and the reaction is carried out in a solid phase polymerization machine.

The resin of the present invention can be used to obtain molded articles (blow molded articles, injection molded articles, sheets, films, etc.) excellent in color tone and transparency by employing blow molding, injection molding, stretching methods, and the like. Fibers can be obtained by melt spinning.

Molded articles containing the resin of the present invention can be produced, for example, by applying various molding methods such as press molding, extrusion molding, air pressure molding and blow molding using raw materials containing the resin of the present invention. This makes it possible to provide various parts including containers. The resin of the present invention has properties close to those of virgin polyester resin and is particularly suitable for the production of blow-molded articles because of its excellent thermal stability. Therefore, it is possible to suitably employ a method for producing a molded article, which includes a step of obtaining a parison from a melt of a raw material containing the resin of the present invention and a step of blowing gas into the parison. Thereby, a molded body such as a container can be manufactured.

A film containing the resin of the present invention can be formed by a known film-forming method using a raw material containing the resin of the present invention. For example, after extruding the melt of the raw material from a T-die, it is cooled with a casting roll to produce an unstretched sheet. Since the resin of the present invention has a relatively low content of foreign matter and excellent thermal stability, it can be stretched in the MD and TD directions with good workability. The stretching method may be uniaxial stretching or biaxial stretching, and the biaxial stretching method may be simultaneous biaxial stretching or sequential biaxial stretching. Then, it is possible to obtain a polyester film having properties such as strength and elongation substantially equal to those obtained when a virgin polyester resin is used, and having excellent transparency.
Although the thickness of the film is not limited, it can usually be appropriately set within the range of 10 to 50 μm. Moreover, if necessary, it can be used as a laminate by being laminated with other layers (for example, an adhesive layer, a heat seal layer, a surface protective layer, a printing layer, a design layer, etc.).

As described above, the resin of the present invention has excellent thermal stability because the content of diethylene glycol and the concentration of carboxyl terminal groups are not more than specific amounts. For this reason, when obtaining the above-mentioned molded article, it is possible to obtain a molded article with a high degree of uniformity with good workability without causing thickness unevenness or the like. Furthermore, as described above, the resin of the present invention has an average pressurization rate of 0.6 MPa/h or less, and contains a small amount of foreign matter. Inorganic substances and foreign substances derived from non-polyester resins are assumed to be the foreign substances present in the resin. can.

In the case of a molded article, a decrease in intrinsic viscosity and a deterioration in color tone after molding can be prevented by containing 0.1 to 1.0% by mass of a hindered phenolic antioxidant.
Further, as will be described later, in the case of molded articles, it is preferable to contain a germanium-based compound and a cobalt compound as polymerization catalysts, and more preferably to contain a dye.

The germanium-based compound is preferably contained in an amount of 5.0×10 ⁻⁵ to 3.0×10 ⁻⁴ mol per 1 mol of the acid component of the polyester. If it is less than 5.0×10 ⁻⁵ mol, it will be difficult to obtain a polyester resin with the desired degree of polymerization. On the other hand, when the amount exceeds 3.0×10 ⁻⁴ mol, by-products resulting from the reaction between the cobalt compound and the germanium compound deteriorate the stability of the polyester over time, resulting in a decrease in the intrinsic viscosity of the polyester resin composition after long-term storage, or This is not preferable because it causes deterioration of color tone.

Germanium-based compounds include germanium dioxide, germanium tetrachloride, germanium tetraethoxide, etc. Germanium dioxide is preferred from the viewpoint of polycondensation catalytic activity, physical properties of the resulting polyester resin, and cost.

The content of the cobalt compound is preferably 1.0×10 ⁻⁵ mol to 1.0×10 ⁻⁴ mol, more preferably 2.0×10 −5 mol to 8.0×10 ⁻⁴ mol, per 1 mol of the acid component of the polyester. It is preferably 0×10 ⁻⁵ mol.
less than 1.0×10 ⁻⁵ mol. Color tone of polyester deteriorates. On the other hand, if the amount exceeds 1.0×10 ⁻⁴ mol, the stability of the polyester resin over time will also deteriorate. Cobalt compounds include cobalt acetate, cobalt formate, cobalt chloride, cobalt oxide, etc. Cobalt acetate is preferred from the viewpoint of polycondensation catalyst activity, physical properties of the obtained polyester resin, and cost.

As for the dye, it is preferable to use the one described above, and the content thereof is preferably 30 ppm or less. If it exceeds 30 ppm, the transparency of the polyester may be lowered and the color may become dull.

In the case of fibers containing the resin of the present invention, the fibers can be produced by, for example, a manufacturing 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 filament fineness of 0.8 dtex or less (preferably 0.6 to 0.3 dtex). 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 properties equivalent to those of virgin polyester resin, so that there is a problem of yarn breakage in any of the melt spinning, drawing / heat treatment, and winding processes. is less likely to occur, and polyester fibers can be obtained with good productivity.

The fibers of the present invention containing the resin of the present invention may be, for example, monofilaments, multifilaments, or the like, and may be long fibers, short fibers, or the like.

Molded articles containing the resin of the present invention include nonwoven fabrics obtained by a spunbond method in which the resin of the present invention is melt-spun, spread and deposited on a net conveyor to form a web, and a nonwoven fabric obtained by melting the resin of the present invention. A nonwoven fabric obtained by a meltblown method in which ultrafine fibers are spun and a web is formed by blowing high-pressure air from the periphery of a spinning nozzle to accumulate ultrafine fibers can be mentioned. Since the resin of the present invention has a low content of foreign matters as described above, it can be melt-spun in a good manner even in the spunbond method or the meltblown method.
In the spunbond method, the filament spun from the spinning nozzle may be cooled using a known cooling device, drawn and thinned using a suction device, and taken off. The speed during traction thinning may be set to about 2500 m to 5000 m/min. Further, the single fiber fineness of the continuous fibers obtained by the spunbond method may be any fineness of about 0.5 to 10 decitex. The web formed by the spunbond method may be made into a nonwoven fabric by general nonwoven fabric forming means such as heat treatment by passing it through a hot embossing roll or the like, or entangling fibers by needle punching or the like.

The content of the resin of the present invention is 50% by mass of the resin constituting the molded article, the film, and the fiber of the molded article containing the resin of the present invention, the film containing the resin of the present invention, and the fiber containing the resin of the present invention. It is preferably 60% by mass or more, more preferably 80% by mass or more, and most preferably 100% by mass. If the proportion of the resin of the present invention in the resin constituting the molded product, film, or fiber is less than 50% by mass, the usage rate of recycled raw materials will be low, making it difficult to produce environmentally friendly products.

When the fiber of the present invention is a staple fiber, it should have characteristic values such as a single filament fineness of 0.1 to 25.0 decitex, a strength of 0.1 to 6.0 cN/dtex, and an elongation of 20 to 500%. can be done. As described above, the resin of the present invention has excellent thermal stability because the content of diethylene glycol and the concentration of carboxyl terminal groups are not more than specific amounts. Therefore, when obtaining the short fibers as described above, fusion of the single yarns in the spinning and drawing processes is suppressed, variation in the fineness of the single yarns is less likely to occur, and fibers with a high degree of uniformity can be obtained with good workability. can. In addition, since fusion of single filaments in the spinning and drawing processes is suppressed, single filament dispersibility in water is improved when used for wet-laid nonwoven fabrics.

Furthermore, as described above, the resin of the present invention has an average pressurization rate of 0.6 MPa/h or less, and contains a small amount of foreign matter. Foreign substances present in the resin are assumed to be inorganic substances and foreign substances derived from non-polyester resins, but by reducing the amount of these foreign substances, the quality and strength of products such as nonwoven fabrics obtained using the fiber of the present invention are improved. do.

In addition, since the resin of the present invention has excellent thermal stability and the amount of foreign matter is small, flow drawing can be performed in the drawing process, and ultrafine fibers with a single filament fineness of 0.1 to 0.03 decitex can be obtained. be able to. Flow drawing is performed at a temperature between the glass transition temperature of the resin used and the crystallization temperature at elevated temperature, and it is possible to reduce the fiber diameter while suppressing the orientation of undrawn fibers. In order to perform more stable flow drawing, it is desirable to draw in a medium having a temperature higher than the glass transition temperature of the polyester to be used by 10°C or more. Further, it is preferable to use water or steam as a medium, and more preferably, the stretching is performed in warm water of 80°C or more and less than 110°C or in wet heat of less than 110°C.

Particles that act as a lubricant during melt spinning of fibers may also be added to the extent that the effects of the present invention are not impaired. The lubricant is preferably inert to the polyester, and examples thereof include titanium oxide, silica, calcium carbonate, barium sulfate, and aluminum oxide. From the viewpoint of smoothness and particle size distribution, titanium oxide is particularly preferred. It is preferable to use By adding a lubricant, single filament fusion can be further suppressed in the spinning and drawing processes, so that when used for wet-laid nonwoven fabrics, single filament dispersibility in water is improved. As for the method of addition, it may be added in any process of the spinning stage of the composite fiber. , a masterbatch system is preferred. In the case of adopting the masterbatch method, there are a method of weighing and mixing at the stage of raw material pellets and melt spinning, and a method of weighing and mixing separately melted polymers and spinning, but any method can be used. good too.

The fibers (staple fibers) of the present invention can be suitably used for nonwoven fabric applications. It may contain fibers other than fibers. For example, a non-woven fabric using the fiber of the present invention as the main fiber and a binder fiber made of a polyester resin having a lower melting point than the resin of the present invention can be used.

The nonwoven fabric obtained using the fiber of the present invention may be dry or wet, and the basis weight of the nonwoven fabric is not particularly limited. When the fiber of the present invention is used as the main fiber, the form of the nonwoven fabric includes thermal bond nonwoven fabric, needle punch nonwoven fabric, airlaid nonwoven fabric, spunlace nonwoven fabric, wet-laid nonwoven fabric (papermaking), and the like. Among them, since the fiber of the present invention can be obtained as a high-quality ultrafine fiber, the nonwoven fabric using the ultrafine fiber as the fiber of the present invention has high quality, uniformity, and excellent porosity, and can be used as a filter for water treatment. It can be suitably used for various industrial filters and separators.

An example is given about the manufacturing method of a dry nonwoven fabric. This is an example of obtaining a dry-laid nonwoven fabric by using the fiber of the present invention as the main fiber and mixing it with a binder fiber other than the fiber of the present invention. The ratio of the fibers of the present invention is preferably about 10 to 90% by mass, although any choice may be made. Both of these fibers (fibers to be constituent fibers) are put into a carding machine and defibrated to produce a dry web. The obtained web is subjected to a heat bonding treatment at a temperature at which the resin constituting the binder fibers melts or softens in a continuous heat treatment machine that performs hot air treatment, to obtain a dry nonwoven fabric in which the constituent fibers are integrated by heat bonding.

An example is given about the manufacturing method of a wet nonwoven fabric. As with the dry-laid nonwoven fabric, this is an example of obtaining a wet-laid nonwoven fabric by using the fibers of the present invention as the main fibers and mixing them with binder fibers other than the fibers of the present invention. The ratio of the fiber of the present invention is preferably about 10 to 90% by mass, although it may be appropriately selected depending on the properties. Both of these fibers (fibers to be constituent fibers) are agitated and fibrillated by using a pulp disintegrator, and then a wet web is produced by a paper machine. The obtained web is subjected to a heat bonding treatment at a temperature at which the resin constituting the binder fibers melts or softens in a continuous heat treatment machine that performs hot air treatment, to obtain a wet-laid nonwoven fabric in which the constituent fibers are integrated by heat bonding.

When the fiber of the present invention is a long fiber, it is possible to obtain an ultrafine fiber having a single filament fineness of 0.8 decitex or less (preferably 0.6 to 0.3 decix) by melt spinning. At this time, using an extruder-type melt spinning machine, the resin of the present invention is melted at a temperature range of 280 to 310° C., spun from a spinning nozzle, and wound at a spinning speed of 500 to 4000 m/min. The obtained undrawn yarn can be obtained by drawing with a drawing device at a drawing temperature of 20 to 200° C. and a drawing ratio of 1.1 to 5.0 times, and winding up (in the case of drawn yarn).

When the fiber of the present invention is not drawn, the resin of the present invention is melted at a temperature of 280 to 310° C., spun from a spinning nozzle, and wound at a spinning speed of 2800 to 8000 m/min. can be obtained (in the case of undrawn yarn, partially oriented undrawn yarn).

Furthermore, when the fiber of the present invention is used as a false twist textured yarn, the fiber wound without drawing as described above is processed at a processing speed of 100 to 700 m / min and a draw ratio of 1.10 to 1. It is preferable to perform false twisting under conditions of .30 times.

EXAMPLES Next, the present invention will be specifically described using examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
[Characteristic values of recycled polyester resin]
(a) Melt Viscosity of Depolymer The depolymer obtained in production step (1) was measured using a VISCO METER DV2T melt viscometer manufactured by Brookfield at the same temperature as the treatment temperature during depolymerization.
(b) Intrinsic viscosity The intrinsic viscosity is measured at a temperature of 20°C using the obtained recycled polyester resin and an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(c) Composition of polyester resin The obtained recycled polyester resin is dissolved in a mixed solvent having a volume ratio of deuterated trifluoroacetic acid and deuterated chloroform of 1/11, and JNM-ECZ400R/S1 manufactured by JEOL Ltd. 1H-NMR was measured with a type NMR apparatus, and from the integrated intensity of the proton peak of each component in the obtained chart, the type and content of the copolymer component were determined.

(d) Carboxyl Terminal Group Concentration Dissolve 0.1 g of the obtained recycled polyester resin in 10 ml of benzyl alcohol, add 10 ml of chloroform to this solution, and titrate with a 1/10 N potassium hydroxide benzyl alcohol solution. rice field.
(e) Average pressurization rate measured by pressurization tester The obtained recycled polyester resin is melted at 300 ° C. in an extruder, and a stainless steel twilled woven filter (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, viscous drag coefficient (m ⁻¹ ) : 2.60 × 10 ⁷ , inertial resistance coefficient: 5.14 × 10, manufactured by Kamijo Seiki Co., Ltd.), and a reinforcing material (stainless steel plain weave wire mesh (nominal size mesh: 40 mesh, Weaving method: plain weave, wire diameter: 0.21 mm (manufactured by Kamijo Seiki Co., Ltd.) After laminating, the polymer discharge rate is set to 29.0 g / min, and the filter pressure is increased using a pressurization tester; "Measured using a detector. The pressure rise test using the pressure test machine was performed continuously for 12 hours, and the initial pressure value (MPa) when starting the pressure rise test (5 to 5 after the polyester resin started passing through the filter The initial pressure is the minimum value of the pressure for 10 minutes.) and the final pressure value (MPa) after 12 hours, the average pressure increase rate was calculated by the following formula.
Average pressure rise rate (MPa/h) = (final pressure value - initial pressure value)/12

(f) Melting point and glass transition temperature The obtained recycled polyester resin is heated (decreased) in a nitrogen stream in a temperature range of 25°C to 280°C using a differential scanning calorimeter (Diamond DSC) manufactured by PerkinElmer. Measurement was performed at a speed of 20°C/min and a sample amount of 8 mg.

[Evaluation of short fibers]
(g) Workability (thread cut)
The operability was evaluated by the number of yarn breaks in the melt spinning process. The case where the number of broken yarns per 1 ton of spinning amount was less than 5 and there was no single yarn adhesion of the obtained short fibers was evaluated as "good", and the other cases were evaluated as "poor".
(h) Dispersibility in Water 1 kg of water at 30°C was weighed into a beaker of 2000 cm ³ , 10 g of the obtained short fibers were added thereto, and stirred with a DC stirrer (stirring propeller was a three-screw type with a diameter of about 50 mm). The number of bundled fibers was visually counted for the dispersed state after stirring under conditions of a rotation speed of 850 rpm and a stirring time of 2 minutes, and evaluated in the following three grades. It should be noted that, if the evaluation was between ◯ and △, it was regarded as acceptable.
Evaluation Number of bundled fibers ○: 1 or less △: 2 to 5 ×: 6 or more (i) Fineness of short fibers Measured according to JIS L1015 8.5.1 B method.

[Characteristic values and evaluation of long fibers]
(j) Strength and elongation Measured according to JIS L 1013 using Tensilon RTC-1210 (manufactured by Orientec).
(k) Number of fluff Using a partially oriented undrawn yarn, the number of fluff (number/10 ⁸ m) was measured using a warping machine. Measurements were made with a fiber length of 3×10 ⁸ m.

(l) Spinnability When obtaining partially oriented undrawn yarn, the state of yarn breakage during melt spinning was evaluated as follows based on the number of yarn breakages per spindle when melt spinning was performed continuously for 24 hours. It was evaluated in 3 stages.
Good: The number of yarn breakages was 0.
Δ: The number of yarn breakage was 1 to 2 times.
x: The number of yarn breakages was 3 or more.
(m) Drawability The state of yarn breakage when drawing a partially oriented undrawn yarn was evaluated in the following three stages according to the number of breaks (total number of times) when drawing was performed continuously for 10 hours with 100 spindles. evaluated.
Good: The number of cuts was 0 to 1.
Δ: The number of cuts was 2 to 4.
x: The number of cuts was 5 or more.

[Evaluation of blow molded product]
(n) Formability The thickness of the body of the obtained container (100 samples) was measured, and the difference between the thickness of the thickest part and the thinnest part was up to 0.30 mm. The number of samples is indicated.
(O) 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 20 was taken as the average value of The smaller this value, the better the transparency, and the value of 6% or less was judged to be excellent in transparency.
(p) Impact resistance (n) A molded product (100 samples) that passed the moldability evaluation was filled with 340 ml of tap water and placed on a P tile at room temperature at a height of 200 cm. Then, the molded body was dropped once with the bottom surface facing downward and the side surface facing downward. At this time, the impact resistance was evaluated by the number of molded bodies that did not crack. In the case of 90 or more, the impact resistance was evaluated as good.

[Evaluation of film]
(q) Tensile strength (MPa)
The tensile strength was measured according to JIS K7127 using a Shimadzu DSS-500 type autograph. Samples were obtained by cutting the central portion in the TD direction of the biaxially stretched polyester resin films obtained in Examples and Comparative Examples into a width of 10 mm and a length of 150 mm in the MD direction and the TD direction, respectively. Measurement was performed under the conditions of a measurement length of 100 mm and a tensile speed of 500 mm/min, and the following equation was obtained.
Tensile strength (MPa) = tensile load at break (N)/average original cross-sectional area of measurement sample (mm ² )

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

(s) Runnability
Evaluation was made according to the following criteria under conditions in which polyester resin films were continuously produced. .largecircle..Operation was possible 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, breakage of the film, contamination of the roll, or the like.

Example 1
[Production of recycled polyester resin]
35.9 parts by mass of a recycled polyester raw material (recycled PET flakes made from used products) was charged into an esterification reactor, and then 4.1 parts by mass of ethylene glycol was added while the stirrer of the esterification reactor was being rotated. . 53.8 parts by mass of recycled polyester raw material (recycled PET flakes made from used products) was added to the esterification reactor (hereinafter referred to as “ES can”) over about 30 minutes from the point where the internal temperature drop stopped. After adding a fixed amount, 6.2 parts by mass of ethylene glycol was additionally added.
At this time, the recycled polyester raw material was added so that the molar ratio of all glycol components/all acid components (hereinafter sometimes referred to as "G/A") was 1.35.
Thereafter, a depolymerization reaction was carried out under heat treatment conditions of 230°C for 1 hour to obtain a depolymer having a melt viscosity of 80 mPa·s at 230°C.
A candle filter with an opening of 20 μm was set between the esterification reactor and the polycondensation reactor, and the obtained depolymerized product was pressure-fed to the polycondensation reactor (hereinafter referred to as a PC can). At this time, the filtrate was collected by passing the depolymerized product through the filter.
In the PC can, the filtrate contained 1.0×10 ⁻⁴ mol per 1 mol of the acid component of the polyester resin to obtain antimony trioxide as a polycondensation catalyst, and 0.2×10 ⁻ of cobalt acetate as a color tone adjusting agent. ⁴ mol and 0.23 parts by mass of titanium dioxide were added and kneaded at a temperature of 270° C. to obtain a reaction product.
Next, the PC can was evacuated and after 60 minutes, a polycondensation reaction was carried out at a final pressure of 0.5 hPa and a temperature of 270° C. for 2.5 hours to obtain a recycled polyester resin (intrinsic viscosity: 0.73).

[Production of staple fibers]
Using the obtained recycled polyester resin, melt spinning was performed using a spinneret with a hole number of 2010H and a hole diameter of 0.18 mm at a discharge rate of 334 g/min, a spinning temperature of 290°C and a spinning speed of 1176 m/min. The obtained undrawn yarn was bundled to form a tow of 80 ktex and drawn under the conditions of a drawing temperature of 60° C. and a drawing ratio of 2.8 times. Next, after applying an oil solution, the tow was squeezed so that the moisture content of the tow was about 18% by mass, and cut into 5 mm lengths with a drum cutter to obtain short-cut fibers with a single filament fineness of 0.5 dtex.

[Manufacturing of long fibers]
The obtained recycled polyester resin was spun by an extruder-type melt spinning machine at a resin temperature of 295° C. through a spinning nozzle (hole diameter 0.15 mm, number of holes 84 holes) equipped with a filter having a filtration particle size of 20 μm, and spinning at 2900 m/min. A multifilament yarn (partially oriented undrawn yarn) having a fineness of 45 dtex was obtained.

Examples 2-7, 11-13, Comparative Examples 1-2, 6-9
[Production of recycled polyester resin]
Example 1 except that the amount of ethylene glycol, recycled polyester raw material, and ethylene terephthalate oligomer added during the depolymerization reaction, G/A, the heat treatment temperature during the depolymerization reaction, and the melt viscosity were changed to those shown in Table 1. A depolymerization reaction was carried out in the same manner as above.
A regenerated polyester resin was produced in the same manner as in Example 1, except that the filtration particle size of the filter in the step of collecting the filtrate and the heat treatment temperature in the polycondensation reaction step were changed to those shown in Table 1.
[Production of staple fibers]
A shortcut fiber having a single filament fineness of 0.5 dtex was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.
[Production of long fibers]
A multifilament yarn (partially oriented undrawn yarn) was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.

Example 8
[Production of recycled polyester resin]
In a twin-screw extruder, 57.7 parts by mass of recycled polyester raw material (recycled PET flakes made from used products) was melted at a melting temperature of 280° C., and 2.0 parts by mass of ethylene glycol was supplied into the extruder.
At this time, the recycled polyester raw material is charged so that the molar ratio of all glycol components / all acid components (hereinafter sometimes referred to as "G / A") is 1.06, and then inside the extruder , under heat treatment conditions of 280°C, 20 decomposition polymerization reactions were carried out to obtain a depolymer having a melt viscosity of 580 mPa·s at 280°C.
A candle filter with an opening of 20 μm was set between the twin-screw extruder and the polycondensation reactor, and the resulting depolymerized product was pressure-fed to the polycondensation reactor (hereinafter referred to as a PC can). At this time, the filtrate was collected by passing the depolymerized product through the filter.
In the PC can, the filtrate was added with 1.0×10 ⁻⁴ mol of antimony trioxide as a polycondensation catalyst per 1 mol of the acid component of the obtained polyester resin, and 0.2×10 −4 mol of cobalt acetate as a color tone adjusting agent ^{. 4} mol and 0.23 parts by mass of titanium dioxide were added and kneaded at a temperature of 280° C. to obtain a reaction product.
Next, the PC can was evacuated and after 60 minutes, polycondensation reaction was carried out at a final pressure of 2 hPa and a temperature of 280° C. for 3.5 hours to obtain a recycled polyester resin (intrinsic viscosity: 0.69).

[Production of staple fibers]
A shortcut fiber having a single filament fineness of 0.5 dtex was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.
[Manufacturing of long fibers]
A multifilament yarn (partially oriented undrawn yarn) was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.

Examples 9-10, Comparative Examples 4-5
The procedure of Example 8 was repeated except that the amounts of ethylene glycol and recycled polyester raw material added during the depolymerization reaction, G/A, the heat treatment temperature during the depolymerization reaction, and the melt viscosity were changed to those shown in Table 1. , a depolymerization reaction was carried out.
Otherwise, the filtrate was recovered from the depolymerized product in the same manner as in Example 8 to obtain a reaction product, which was subjected to a polycondensation reaction to obtain a regenerated polyester resin (intrinsic viscosity: 0.69).
In Comparative Example 5, since the melt viscosity of the depolymer obtained by the depolymerization reaction was too high, a filter could not be added in the next step, and a recycled polyester resin could not be obtained.

[Production of staple fibers]
A shortcut fiber having a single filament fineness of 0.5 dtex was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.
[Manufacturing of long fibers]
A multifilament yarn (partially oriented undrawn yarn) was obtained in the same manner as in Example 1, except that the obtained recycled polyester resin was used.

Table 1 shows the characteristic values of the recycled polyester resins obtained in Examples 1 to 13 and Comparative Examples 1 to 9, and the characteristic values and evaluation results of the short fibers and long fibers obtained using these recycled polyester resins.

As is clear from Table 1, the recycled polyester resins obtained in Examples 1 to 13 had a carboxyl terminal group content, a diethylene glycol content, and an average pressurization rate within the ranges specified in the present invention. Both fibers and long fibers could be obtained with good workability. The obtained short fibers were excellent in dispersibility in water. Moreover, the obtained filament was a multifilament yarn excellent in both strength and elongation and having no fluff.

On the other hand, in Comparative Example 1, since the G/A during the depolymerization reaction was high, the recycled polyester resin obtained had a high content of diethylene glycol and a high average pressurization rate. As a result, the operability in obtaining short fibers and long fibers was poor, resulting in inferior quality and characteristic values.
In Comparative Example 2, since the melt viscosity of the obtained depolymer was too low, the filtrate leaked when passing through the filter in the filtration step, and the next step could not be performed.
In Comparative Example 3, since the G/A at the time of the depolymerization reaction was low, the resulting recycled polyester resin had a high carboxyl terminal group concentration and a high average pressurization rate. As a result, the operability in obtaining short fibers and long fibers was poor, resulting in inferior quality and characteristic values.
In Comparative Example 4, the depolymerization step was carried out under heat treatment conditions of 290° C., so the obtained recycled polyester resin had a high carboxyl terminal group concentration. As a result, the operability in obtaining short fibers and long fibers was poor, resulting in inferior quality and characteristic values.

In Comparative Example 5, the melt viscosity of the obtained depolymerized polymer was too high, so that it was difficult to pass through the filter in the filtration step, and it was not possible to proceed to the next step.
In Comparative Example 6, the heat treatment temperature in the depolymerization step was low, and the melt viscosity of the depolymer obtained in the depolymerization step was too high. I couldn't do it.
In Comparative Example 7, since the filtration particle size of the candle filter provided between the ES can and the PC can was 35 μm, the obtained regenerated polyester resin had a high average pressurization rate. As a result, the operability in obtaining short fibers and long fibers was poor, resulting in inferior quality and characteristic values.
In Comparative Example 8, since the filtration particle size of the candle filter provided between the ES can and the PC can was 5 μm, it was difficult to pass through the filter, and it was not possible to proceed to the next step.
In Comparative Example 9, since the polycondensation reaction temperature in the polycondensation step was too low, the polymerization rate was slow and a recycled polyester resin could not be obtained.

Example 14
[Production of staple fibers]
Using the recycled polyester resin described in Example 2, melt spinning was performed using a spinneret with a hole number of 2010H and a hole diameter of 0.18 mm at a discharge rate of 210 g/min, a spinning temperature of 290°C and a spinning speed of 1176 m/min. The obtained undrawn yarn was bundled to form a tow of 80 ktex and drawn under the conditions of a drawing temperature of 60° C. and a drawing ratio of 2.8 times. Next, after applying an oil solution, the tow was squeezed so that the moisture content of the tow was about 18% by mass, and cut into 5 mm lengths with a drum cutter to obtain short-cut fibers with a single filament fineness of 0.3 dtex.
The obtained short-cut fiber was evaluated as ◯ in the short fiber production workability (cut yarn) evaluation, and was also evaluated as ◯ in the water dispersibility evaluation.

Example 15
[Production of staple fibers]
Using the recycled polyester resin described in Example 2, melt spinning was performed using a spinneret with a hole number of 2010H and a hole diameter of 0.18 mm at a discharge rate of 160 g/min, a spinning temperature of 290°C and a spinning speed of 1176 m/min. The obtained undrawn yarn was bundled to form a tow of 80 ktex, and flow drawing was performed in hot water at 85° C. at a draw ratio of 4.0 times. Next, after applying an oil agent, the tow was squeezed so that the moisture content of the tow was about 18% by mass, and cut into 5 mm lengths with a drum type cutter to obtain short-cut fibers with a single filament fineness of 0.1 dtex.
The obtained short-cut fiber was evaluated as ◯ in the short fiber production workability (cut yarn) evaluation, and was also evaluated as ◯ in the water dispersibility evaluation.

Example 16
[Manufacturing of blow-molded products]
The recycled polyester resin (intrinsic viscosity 0.73) obtained in Example 1 is continuously supplied to a crystallizer, crystallized at 150°C, supplied to a dryer, and dried at 175°C for 4 hours. After that, it is sent to a preheating machine, heated to 210 ° C., then supplied to a solid phase polymerizer, and solid phase polymerization reaction is performed at 210 ° C. for 25 hours in a nitrogen gas atmosphere to produce a recycled polyester resin with an intrinsic viscosity of 1.21. got
After chipping the recycled polyester resin obtained by the solid phase polymerization reaction and drying it, the resin is extruded at an extrusion temperature of 280° C. using a direct blow molding machine (manufactured by Tahara Co., Ltd.) to form a cylindrical parison. While it was in a softened state, it was sandwiched between molds to form a bottom, and then blown to form a bottle. At this time, when the parison had a diameter of 3 cm and a length of 25 cm, the bottom was formed and blow-molded to obtain a 350-ml hollow container (direct blow molded product).

Example 17
A solid-phase polymerization reaction was carried out in the same manner as in Example 16 except that the recycled polyester resin obtained in Example 8 was used to obtain a recycled polyester resin having an intrinsic viscosity of 1.19.
A hollow container was obtained by blow molding in the same manner as in Example 16, except that a recycled polyester resin obtained by a solid phase polymerization reaction was used.

Comparative example 10
A solid-phase polymerization reaction was carried out in the same manner as in Example 16 except that the recycled polyester resin obtained in Comparative Example 1 was used to obtain a recycled polyester resin having an intrinsic viscosity of 1.19.
A hollow container was obtained by direct blow molding in the same manner as in Example 16, except that a recycled polyester resin obtained by a solid phase polymerization reaction was used.

Comparative example 11
A solid-phase polymerization reaction was carried out in the same manner as in Example 16 except that the recycled polyester resin obtained in Comparative Example 4 was used to obtain a recycled polyester resin having an intrinsic viscosity of 1.19.
A hollow container was obtained by direct blow molding in the same manner as in Example 16, except that a recycled polyester resin obtained by a solid phase polymerization reaction was used.

Table 2 shows the evaluation results of moldability, haze and impact resistance of the hollow containers obtained in Examples 16-17 and Comparative Examples 10-11.

As is clear from the results in Table 2, the hollow containers obtained in Examples 16 and 17 can be obtained with good moldability, and the obtained hollow containers have low haze and excellent transparency, and are resistant to It was also excellent in shock resistance.
On the other hand, in Comparative Example 10, a recycled polyester resin having a high diethylene glycol content and a high average pressurization rate was used, resulting in poor moldability, and the resulting hollow container was poor in both transparency and impact resistance. there were. In Comparative Example 11, since a recycled polyester resin having a high carboxyl terminal group concentration was used, moldability was poor, and the resulting hollow container was poor in both transparency and impact resistance.

Example 18
[Film production]
93.5% by mass of the recycled polyester resin (intrinsic viscosity 0.73) obtained in Example 1 and 6.5% by mass of a polyethylene terephthalate resin containing 1.5% by mass of silica particles as a master chip were mixed, and both The resin is melted and kneaded in an extruder, supplied to a T-die, discharged in sheet form, wound around a metal drum temperature-controlled at 20°C, cooled and wound up to produce an unstretched sheet with a thickness of about 150 μm. bottom. Next, the ends of this unstretched sheet were held by clips of a tenter-type simultaneous biaxial stretching device, and under the conditions of 180° C., it was simultaneously stretched at a stretching ratio of 3.0 times in the MD direction and 3.3 times in the TD direction. After being biaxially stretched, the film was heat-treated at 215° C. for 4 seconds at a relaxation rate of 5% in the TD direction, slowly cooled to room temperature, corona-discharged on one side, and wound up. Thus, a biaxially stretched polyester resin film having a thickness of 15 μm was obtained.

Example 19
An unstretched sheet was produced in the same manner as in Example 18, except that the recycled polyester resin obtained in Example 4 was used. A resin film was obtained.

Comparative example 12
An attempt was made to produce an unstretched sheet in the same manner as in Example 18, except that the recycled polyester resin obtained in Comparative Example 3 was used. As a result, two hours after the start of the operation, the production was stopped, and the unstretched sheet could not be subjected to the stretching process, so that the biaxially stretched polyester resin film could not be obtained.

Comparative example 13
An unstretched sheet was produced in the same manner as in Example 18 except that the recycled polyester resin obtained in Comparative Example 1 was used, and the stretching heat treatment was performed in the same manner as in Example 18 to obtain a biaxially stretched polyester having a thickness of 12 μm. A resin film was obtained. However, for the same reason as in Comparative Example 12, the continuous operation could not be continued for 24 hours or more, and production was not possible in 14 hours.

Table 3 shows the evaluation results of the tensile strength, haze and runnability of the films obtained in Examples 18-19 and Comparative Examples 12-13.

As is clear from the results in Table 3, the biaxially stretched polyester resin films obtained in Examples 18 and 19 have high tensile strength in both the MD and TD directions, have low haze and excellent transparency, and are virgin polyester. It had characteristic values comparable to those of films made of resin. Furthermore, the operability was also good.
On the other hand, in Comparative Example 12, since a recycled polyester resin having a high carboxyl terminal group concentration and a high average pressurization rate was used, the workability was poor, and a biaxially stretched polyester resin film could not be obtained.
In Comparative Example 13, since a recycled polyester resin with a high content of diethylene glycol was used, the workability was poor, and the resulting biaxially stretched polyester resin film was poor in both tensile strength and haze.

Claims (5)

A polyester resin containing 80% by mass or more of a component derived from at least one recycled polyester raw material of a) used polyester products and b) unadopted polyester resin generated in the process of manufacturing polyester products, A recycled polyester resin characterized by satisfying all of 1) to (3).
(1) When the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less,
(2) a carboxyl terminal group concentration of 40 equivalents/t or less;
(3) The average pressurization rate is 0.6 MPa / h or less (however, the average pressurization rate is a value calculated by the following procedure: Using a pressurization tester including an extruder and a pressure sensor, the extruder Stainless steel filter at the tip (nominal size mesh: 1400 mesh, weaving method: twilled dutch, 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 pressure value applied to the filter when extruding the melt at a discharge rate of 29.0 g / min from the filter is the start of extrusion. If the pressure value at the time of extrusion is defined as "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is defined as "final pressure value (MPa)", the following calculation is based on those pressure values. Calculate the average pressure rise rate by Equation A:
Average pressure increase rate (MPa/h) = (final pressure value - initial pressure value) / 12) ... A) A molded article containing the recycled polyester resin according to claim 1 . A fiber containing the recycled polyester resin of 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 a) a used polyester product and b) an unused polyester resin generated in the process of producing a polyester product, the method comprising the following (1) to ( 4) A method for producing a recycled polyester resin, comprising all of the steps.
(1) Ethylene glycol is added to the raw material so that the total glycol component/total acid component molar ratio is 1.04 to 1.40, and depolymerization is performed under heat treatment conditions of 220 to 285°C. (2) passing the depolymer through a filter having a filtration particle size of 10 to 25 μm to collect a filtrate (3) adding a polycondensation catalyst to the filtrate; and kneading to obtain a reaction product;