JP2022047520A - Recycled polyester resin and method for producing recycled polyester resin - Google Patents

Abstract

To provide a recycled polyester resin that includes components derived from recycled polyester materials including used polyester products, or scrap or the like occurring in the process of producing polyester resins and products.SOLUTION: The present invention discloses a polyester resin that includes components derived from at least one recycled polyester material of a) used polyester products, or b) rejected polyester occurring in the process of producing polyester products. (1) The recycled polyester resin includes a phosphorus compound, with the polyester resin having a phosphorus content of 1000-10000 ppm. (2) When the total content of all glycol components is 100 mol%, ethylene glycol is 80 mol% or more and diethylene glycol is 4 mol% or less. (3) The carboxyl end group content is 40 equiv./t or less. (4) The 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 having flame retardancy and a method for producing a recycled polyester resin. In particular, the present invention is manufactured using a recycled polyester raw material derived from a used polyester product and a recycled polyester raw material derived from an unadopted polyester resin 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 and a method for producing the same, as in the case of the virgin polyester resin.

Polyethylene terephthalate (hereinafter, may be abbreviated as PET) is widely used for molded products such as fibers, films, and PET bottles because of its high melting point, chemical resistance, and relatively low cost. ..
These polyester products inevitably generate waste at the manufacturing and processing stages, and are often disposed of after use.However, when incinerating, high heat is generated, so the incinerator is severely damaged and has a long life. There is a problem that becomes shorter. 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 were thrown away as garbage flowed out into the ocean via rivers, and microplastics that were finely crushed by the action of waves and tidal currents accumulated in the bodies of marine organisms. Concentrated in the food chain, which has an adverse effect on the ecosystem of marine organisms, and the fact that plastics are a major cause of marine pollution have been regarded as problems, and all movements to reduce usage and switch to biodegradable plastics have been made. It's happening worldwide.

From the viewpoint of reducing the amount of such plastic products used and from the viewpoint of environmental problems, recycling that reuses resources is carried out by various methods. With regard to polyester products, methods of recycling polyester waste generated in the manufacturing process and methods of collecting and reusing products that have been once on the market and discarded are being studied. In particular, in recent years, with regard to textile products, products bearing the Eco Mark, which is certified by achieving a certain recycling rate, have become widespread.

Various methods have been proposed as a method for recycling recycled polyester raw materials. 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 of adding EG to PET waste and depolymerizing it, and then adding methanol to recover DMT (Patent Document 2). PET waste is depolymerized with EG to form an oligomer, which is used for the polycondensation reaction. A method (Patent Document 3) and the like have been proposed.

In addition, when regenerating PET bottles that have become products once, the problems are the additives added to the polyester resin and the caps (aluminum, polypropylene, polyethylene) and inner plugs that are attached to the bottle body. Liners (polypropylene, polyethylene), labels (paper, polystyrene and other resins, inks), adhesives, printing inks, etc.
As a pretreatment for the regeneration process, first, the collected PET bottles are subjected to a vibration sieve to remove sand, metal and the like. Then, the PET bottle is washed, the colored bottle is separated, and then rough pulverization is performed. Then, the label etc. 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. Components such as adhesives, proteins and molds are removed by high-temperature alkaline cleaning, and dissimilar components such as polypropylene and polyethylene are separated by specific gravity.

However, even through these steps, it has been difficult to separate the non-polyester resin such as polypropylene, polyethylene, and polystyrene as described above from the PET resin. Therefore, even if the recycled polyester resin is obtained by the recycling methods 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 the foreign matter mixed can be sufficiently reduced. It was not possible to obtain a product having the same quality as the virgin polyester resin. 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.

Further, the invention described in Patent Document 4 describes a method of depolymerizing polyester waste with ethylene glycol, filtering it with a filter having an average opening of 10 to 50 μm, and then performing a repolymerization reaction. It has been shown that the obtained recycled polyester resin has a small amount of foreign matter mixed in and is excellent in operability during processing. However, even in this method, the foreign matter derived from the non-polyester resin as described above could not be sufficiently removed, and the amount of the foreign matter mixed could not be sufficiently reduced.

Furthermore, in recent years, there has been an increasing demand for flame-retardant synthetic fibers and various plastic products from the viewpoint of fire prevention.
Conventionally, various attempts have been made to impart flame retardancy to polyester, but from the viewpoint of performance and productivity, a method of copolymerizing a flame retardant substance at the time of polyester production is common. As the flame-retardant-imparting substance used for this purpose, phosphorus compounds are considered to be advantageous from the viewpoints of flame-retardant performance, cost, environmental pollution, and safety. A polyester resin obtained by copolymerizing such a phosphorus compound to impart flame retardancy and having the same performance as that of virgin polyester while using recycled polyester as a raw material has not yet been proposed.

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

INDUSTRIAL APPLICABILITY The present invention is a recycled polyester resin containing a component derived from a recycled polyester raw material containing a used polyester product or a polyester resin and scraps generated in the process of manufacturing the product by solving the above-mentioned problems. It is an object of the present invention to provide a recycled polyester resin which has flammability and has the same performance as a virgin polyester resin and can be used for manufacturing various forms of polyester products. Another object of the present invention is to provide a manufacturing method capable of obtaining such a recycled polyester resin of the present invention.

As a result of diligent research in view of the problems of the prior art, the present inventors have made a manufacturing process using recycled polyester raw materials through a specific manufacturing process, so that the amount of foreign matter mixed is small, which is equivalent to that of virgin polyester resin. It has been found that a recycled polyester resin having the above-mentioned performance and flame retardancy can be obtained, and the present invention has been completed.

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

(A) A recycled polyester resin containing a component derived from at least one recycled polyester raw material of a) used polyester product and b) an unadopted polyester resin generated in the process of manufacturing the polyester product.
(1) It contains a phosphorus compound, and the content of phosphorus atoms in the polyester resin is 1000 to 10000 mass ppm.
(2) When the total amount of all glycol components is 100 mol%, ethylene glycol is 80 mol% or more and diethylene glycol is 4 mol% or less.
(3) The carboxyl terminal group concentration is 40 equivalents / t, and the concentration is 40 equivalents / t.
(4) The average boosting speed is 0.6 MPa / h or less (however, the average boosted speed is a value calculated by the following procedure: using a booster 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 grain 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. When the pressure value at the time is "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is "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 that.
(B) A molded product containing the recycled polyester resin described in (a).
(C) Fiber containing the recycled polyester resin according to (a).
(D) 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 resin generated in the process of manufacturing the polyester product.
(1) A recycled polyester raw material is added to a mixture containing an ethylene terephthalate oligomer, ethylene glycol and a phosphorus compound so that the molar ratio of the total glycol component / total acid component is 1.06 to 1.20, and 245 to 280. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under heat treatment conditions at ° C.
(2) A step of passing the reaction product through a filter having a filtration particle size of 10 to 25 μm and collecting the filtrate.
(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 250 ° C. or higher and 1.0 hPa or lower. ..

The recycled polyester resin of the present invention contains a component derived from at least one recycled polyester raw material of a) used polyester product and b) unadopted polyester resin generated in the process of manufacturing the polyester product, but has a foreign substance. Since the amount of contamination is small and the carboxyl end group concentration and diethylene glycol content satisfy a specific range, it is excellent in thermal stability, and because it contains a phosphorus compound, it is also excellent in flame retardancy. .. For this reason, for example, in the process of obtaining fibers by melt spinning, the process of obtaining a sheet or film by film formation, 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. Therefore, it is possible to manufacture a product having flame retardancy.
Further, according to the method for producing a 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 requiring complicated processes and equipment, which has a practical merit. It's a big one.

Hereinafter, the present invention will be described in detail.
The recycled polyester resin of the present invention (hereinafter, may be referred to as the resin of the present invention) is a recycled polyester raw material of at least one of a) used polyester products and b) unadopted polyester generated in the process of manufacturing polyester products. It contains a component derived from. That is, 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 such as a PET bottle or a packaging material.
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. , Waste generated during molding, processing, etc., cut products of transition products generated at the time of brand change, cut products of prototypes / defective products, etc.

The forms of a) and b) are not limited, and may be pelletized by further processing such as crushing or cutting as necessary, or 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, a mixed product of crystalline pellets and amorphous pellets, and the like can be used. In the present invention, it is particularly preferable to use a crystalline recycled polyester raw material for the purpose of preventing fusion of pellets to each other during charging into a can or depolymerization reaction. Therefore, the material of the above a) or b) crystallized by heat treatment (crystallized pellets or the like) can be preferably used.

The properties of the recycled polyester raw materials of a) and b) are not limited, and the forms of a) and b) may be used as they are, and the cut pieces obtained by further processing such as cutting and crushing may be used. In addition to crushed products (powder) and the like, solid forms such as molded bodies (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 pieces 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 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 charged into a can as a melt.

The recycled polyester resin of the present invention preferably contains 40% by mass or more of a component derived from the recycled polyester raw material, which is at least one of the above a) and b), and more preferably 50% by mass or more.
If the content of the component derived from the recycled polyester raw material is less than 40% by mass, the purpose of considering the environmental problem cannot be achieved. The upper limit of the content of the component derived from the recycled polyester raw material is not particularly limited, but according to the production method of the present invention described later, the content of the component derived from the recycled polyester raw material is 40 to 80% by mass. It is possible to easily obtain recycled polyester resin.

The resin of the present invention contains a phosphorus compound (hereinafter, may be referred to as a phosphorus compound (Y)), and the content of phosphorus atoms in the polyester resin is 1000 to 10000 ppm. As the phosphorus compound (Y), a metal salt of the phosphorus compound is preferable, and a phosphinic acid metal salt compound is preferable from the viewpoint of dispersibility, bleed-out and the like.
Further, as the phosphorus compound, an organic phosphorus compound is preferable, and an organic phosphorus compound having two or more ester-forming functional groups is particularly preferable. As such an organic phosphorus compound, the compound represented by the following formula (1) is preferable from the viewpoint of the reactivity of the polycondensation reaction, the residual ratio of the phosphorus compound and the like.

ただし、Ｒ１は炭素数１～１２のアルキル基又はアリール基を示し、Ｒ２は炭素数１～１８のアルキル基、アリール基、モノヒドロキシアルキル基あるいはＲ１を介した環状体又は水素原子を示し、Ｒ３は炭素数１～１８のアルキル基、アリール基、モノヒドロキシアルキル基又は水素原子を示し、Ａは２価以上の炭化水素基を表す。また、ｎは、Ａの価数から１を引いた数を表す。

However, R1 represents an alkyl group or an aryl group having 1 to 12 carbon atoms, R2 represents an alkyl group having 1 to 18 carbon atoms, an aryl group, a monohydroxyalkyl group or a cyclic body or a hydrogen atom via R1 and R3. Represents an alkyl group having 1 to 18 carbon atoms, an aryl group, a monohydroxyalkyl group or a hydrogen atom, and A represents a hydrocarbon group having a valence of 2 or more. Further, n represents a number obtained by subtracting 1 from the valence of A.

Preferred specific examples of the organic phosphorus compound represented by the above formula (1) include the following structural formulas (a) to (d). Of these, the compound of structural formula (a) is particularly preferable in terms of flame retardancy. These may be either as-is or esterified.

Further, as the phosphinic acid metal salt compound, the phosphinic acid metal salt represented by the following formulas (2) and (3) is preferable.

ただし、式中、Ｒ１及びＲ２は、同一かまたは異なり、メチル、エチル、ｎ－プロピル、イソプロピル、ｎ－ブチル、ｔｅｒｔ－ブチル、ｎ－ペンチル及び／またはフェニルである。Ｒ３は、メチレン、エチレン、ｎ－プロピレン、イソプロピレン、ｎ－ブチレン、ｔｅｒｔ－ブチレン、ｎ－ペンチレン、ｎ－オクチレンもしくはｎ－ドデシレン；フェニレンもしくはナフチレン；メチルフェニレン、エチルフェニレン、ｔｅｒｔ－ブチルフェニレン、メチルナフチレン、エチルナフチレンもしくはｔｅｒｔ－ブチルナフチレン；フェニルメチレン、フェニルエチレン、フェニルプロピレン、もしくはフェニルブチレンである。Ｍは、Ｍｇ、Ｃａ、Ａｌ、Ｓｂ、Ｓｎ、Ｇｅ、Ｔｉ、Ｆｅ、Ｚｒ、Ｚｎ、Ｃｅ、Ｂｉ、Ｓｒ、Ｍｎ、Ｌｉ、Ｎａ、Ｋまたはプロトン化された窒素塩基（プロトン化された窒素塩基とは、好ましくは、アンモニア、メラミン及びトリエタノールアミンのプロトン化された塩基、特にＮＨ４＋を意味する））である。ｍは、１～４であり、ｎは、１～４であり、そしてｘは、１～４である。Ｒ１、Ｒ２、Ｒ３、Ｍ、ｍ、ｎ、及びｘのうちの１つ以上が異なる化合物を混合して用いることも出来る。

However, in the formula, R1 and R2 are the same or different, and are methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl and / or phenyl. R3 is methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene or n-dodecylene; phenylene or naphthylene; methylphenylene, ethylphenylene, tert-butylphenylene, methyl. Naftylene, ethylnaphthylene or tert-butylnaphthylene; phenylmethylene, phenylethylene, phenylpropylene, or phenylbutylene. M is Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Zn, Ce, Bi, Sr, Mn, Li, Na, K or a protonated nitrogen base (protonated nitrogen base). Is preferably a protonated base of ammonia, melamine and triethanolamine, especially NH4 +)). m is 1-4, n is 1-4, and x is 1-4. Compounds in which one or more of R1, R2, R3, M, m, n, and x are different can also be mixed and used.

By containing the phosphorus compound so that the content of the phosphorus atom in the polyester resin is 1000 to 10000 ppm, flame retardancy can be imparted to the polyester resin, and the molded product or fiber having flame retardancy can be imparted. Can be obtained.
The content of the phosphorus atom in the polyester resin is 1000 to 10000 ppm, and more preferably 2000 to 7000 ppm.

If the phosphorus atom content is less than 1000 ppm, the flame retardant performance will be inferior. On the other hand, if the phosphorus atom content exceeds 10,000 ppm, blocking and fusion are likely to occur during high-temperature drying, and the dispersibility of the agent is lowered and bleed-out is likely to occur. Can't be done.

The content of the phosphorus atom in the polyester resin can be kept in the above range by adjusting the amount of the phosphorus compound (Y) contained in the polyester resin.
In the present invention, as a method of containing the phosphorus compound (Y) in the polyester resin, a method of copolymerizing the phosphorus compound (Y) at the time of polymerization to obtain the regenerated polyester resin and a method of copolymerizing the phosphorus compound (Y) after obtaining the regenerated polyester resin are performed. Examples thereof include a method of blending the compound (Y). A more specific method will be described in detail in the description of the manufacturing method.

The acid component (100 mol%) of the resin of the present invention preferably has a terephthalic acid ratio of 80 to 98 mol%, and more preferably 85 to 97 mol%. When the proportion of terephthalic acid is less than 80 mol%, the crystallinity of the resin composition is lowered and it tends to be amorphous. On the other hand, when the ratio of terephthalic acid exceeds 98 mol%, the copolymerization amount (content) of the phosphorus atom becomes small when the phosphorus compound is copolymerized, so that the flame-retardant effect becomes small.

Examples of the acid component other than the terephthalic acid and the phosphorus compound 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 of these may be used in combination, or ester-forming derivatives of these acids may be used.

In the resin of the present invention, when the total amount of the total glycol components is 100 mol%, ethylene glycol is 80 mol% or more of the total glycol components, and more preferably 90 mol% or more. When the content of ethylene glycol is less than 80 mol%, the crystallinity and heat resistance of the obtained polyester resin are inferior.

Further, in the resin of the present invention, when the total amount of all glycol components is 100 mol%, the content of diethylene glycol is 4 mol% or less, and more preferably 3 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 has excellent thermal stability because the content of diethylene glycol is 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.

In the resin of the present invention, examples of the diol component other than ethylene glycol and diethylene glycol in the total glycol component include neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. 1,4-Cyclohexanedimethanol, diethylene glycol, dimerdiol, ethylene oxide adduct of bisphenol S, ethylene oxide adduct of bisphenol A and the like can be used.

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, although it is not limited. 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 1 × 10 ^-5 mol or more, and more than 6 × 10 ^-5 mol, for example, 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 thereto.

Since the polycondensation catalyst contained in the recycled polyester raw material may also act as a catalyst during the polycondensation reaction, the polycondensation contained in the recycled polyester raw material is used when the polycondensation catalyst is added in the polycondensation step. It is preferable to consider the type of catalyst and its content.

Further, at the time of the polycondensation reaction, if necessary, the fatty acid ester capable of adjusting the melt viscosity, the hindered phenolic antioxidant, and the thermal decomposition of the resin can be suppressed 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, dipentaerythritol hexastearate and the like. Among these, glycerin monostearate, pentaerythritol tetrastearate, and dipentaerythritol hexastearate are preferable. These can be used in one kind or two or more kinds.

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, Tetrax [Methyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] Methyl, 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 in one kind or two or more kinds.

As the phosphorus compound, those other than the phosphorus compound (Y) as described above can be used, for example, phosphoric acid, phosphoric acid, trimethylphosphite, triphenylphosphite, tridecylphosphite, trimethylphosphate, tri. Phosphoric compounds such as decylphosphate and triphenylphosfort can be used. These can be used in one kind or two or more kinds. Further, these contents are set so that the content of phosphorus atoms in the polyester resin is in the range of 1000 to 10000 ppm.

The resin of the present invention has the above-mentioned composition and the characteristic values shown below.
(A) Concentration of carboxyl terminal groups is 40 equivalents / t or less (b) Average boosting speed measured by a booster tester is 0.6 MPa / h or less The resin of the present invention having these characteristic values is the production method of the present invention described later. Can be obtained by

First, as the characteristic value of (a), the resin of the present invention preferably has a carboxyl-terminal group concentration of 40 equivalents / t or less, more preferably 30 equivalents / t or less, and further preferably 25 equivalents / t or less. preferable.
The resin of the present invention has excellent heat resistance because the carboxyl terminal group concentration is 40 equivalents / t or less, and a molded product having excellent heat resistance can be obtained with good productivity by various molding methods. Is possible.

The ultimate viscosity of the regenerated polyester resin of the present invention is not particularly limited, but is usually preferably about 0.44 to 0.80. The ultimate 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 boosting speed of 0.6 MPa / h or less, preferably 0.5 MPa / h or less, particularly 0.4 MPa / h, as measured by the following method. The following is preferable. The average step-up rate in the present invention is an index of a large amount of foreign substances derived from various inorganic substances and non-polyester resin, and the smaller the average step-up rate, the smaller the amount of foreign substances mixed. It shows. The lower limit of the average boosting speed can be, for example, about 0.01 MPa / h, but is not limited to this.

To measure the average boosting speed, use a booster tester including an extruder and a pressure sensor, and use a stainless steel filter (nominal dimension 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, Filter particle size: 12 μm), melt the polyester resin at 300 ° C. with an extruder, and discharge 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 extruding is set to "initial pressure value (MPa)", and then continuously extruded for 12 hours. When the pressure value is set to the "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)

By adopting the production method described later, the resin of the present invention can reduce the amount of foreign matter derived from various inorganic substances and foreign matter derived from non-polyester resin, so that by-production of diethylene glycol can be suppressed and (a). ), It becomes possible to obtain a recycled polyester resin satisfying the characteristic values of (b).

The method for producing the resin of the present invention will be described. The method for containing the phosphorus compound (Y) in the polyester resin includes a method of copolymerizing the phosphorus compound (Y) at the time of polymerization to obtain a regenerated polyester resin (hereinafter, may be referred to as production method 1) and a method of regenerating. Examples thereof include a method of blending a phosphorus compound (Y) after obtaining a polyester resin (hereinafter, may be referred to as a production method 2).

[Manufacturing method 1]
First, the above-mentioned manufacturing method 1 will be described. According to the production method 1, the phosphorus compound can be copolymerized in the acid component constituting the polyester resin.
In the production method 1 of the present invention, it is important to carry out the steps shown in (1) to (3) in order.
(1) A recycled polyester raw material is added to a mixture containing an ethylene terephthalate oligomer, ethylene glycol and a phosphorus compound so that the molar ratio of the total glycol component / total acid component is 1.06 to 1.20, and 245 to 280. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under heat treatment conditions at ° C.
(2) A step of passing the reaction product through a filter having a filtration particle size of 10 to 25 μm and collecting the filtrate.
(3) A step of adding a polymerization catalyst to the filtrate and performing a polycondensation reaction at a temperature of 250 ° C. or higher and a reduced pressure of 1.0 hPa or lower.

First, in the depolymerization step (1), a recycled polyester raw material is added to a mixture containing an ethylene terephthalate oligomer, ethylene glycol, and an erin compound, and the molar ratio of the total glycol component / total acid component is 1.06 to 1.20. The reaction product containing the depolymerized product is obtained by depolymerizing under heat treatment conditions of 245 to 280 ° C.

As the ethylene terephthalate oligomer, ethylene glycol and phosphorus compound, known or commercially available ones can be used. It can also be manufactured by a known manufacturing 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 mixture containing ethylene terephthalate oligomer, ethylene glycol and phosphorus compound (hereinafter, may be referred to as mixture E) may be 20 to 80% by mass in 100% by mass of the finally obtained recycled polyester resin. It is preferably 30 to 70% by mass, more preferably 30 to 70% by mass.

When the amount of the mixture E is smaller than the above, when the recycled polyester raw materials are added, the recycled polyester raw materials tend to block each other, which is not preferable because an excessive load is applied to the stirrer.
On the other hand, when the amount of the mixture E 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 is low, which is not preferable.

The ratio of ethylene terephthalate oligomer, ethylene glycol, phosphorus compound, and recycled polyester raw material added in the step (1) may be appropriately changed depending on the intended use in the polyester resin to be finally obtained, but is generally as follows. It is preferable to add in a proportion of (100 parts by mass in total). It is preferable that the ethylene terephthalate oligomer is 5 to 50 parts by mass, the ethylene glycol is 1 to 10 parts by mass, the phosphorus compound is 3 to 10 parts by mass, and the recycled polyester raw material is 40 to 80 parts by mass.

Above all, the amount of ethylene glycol added is preferably 1 to 18 parts by mass, and more preferably 1 to 10 parts by mass in order to sufficiently proceed the depolymerization reaction. If the amount of ethylene glycol added exceeds 18 parts by mass, the ethylene terephthalate oligomer tends to solidify in the reactor, and the subsequent reaction may not be continued, which is not preferable.
When ethylene glycol is added to the ethylene terephthalate oligomer in the mixture E, it is preferable to make the temperature of the contents uniform while turning the stirrer and then add the ethylene glycol in order to prevent the oligomer from solidifying.

When the recycled polyester raw material is added to the mixture E in the step (1), the molar ratio of the total glycol component / total acid component is 1.06 to 1.20 while stirring, and the temperature is 245 to 280 ° C. Depolymerization is performed under the heat treatment conditions of.
This step is important in the production method 1 of the present invention. That is, in the conventional method using a recycled polyester raw material, depolymerization is performed using only the recycled polyester raw material, but in the present invention, the recycled polyester raw material is present in the presence of an ethylene terephthalate oligomer, an ethylene glycol, and a phosphorus compound. In the mixture E, the recycled polyester raw material is added so that the molar ratio of the total glycol component / total acid component is 1.06 to 1.20 for all the components of the recycled polyester raw material. , Depolymerization is performed.

By performing the step (1) as described above, not only various inorganic substances but also foreign substances derived from non-polyester resin can be efficiently deposited. Therefore, in the step (2), these foreign substances are completely filtered. be able to. In the polycondensation reaction of the step (3), the characteristic values of the present invention are that the content (copolymerization amount) of diethylene glycol and the concentration of the carboxyl terminal group are less than a specific amount, and the amount of foreign matter mixed is small. It becomes possible to obtain a recycled polyester resin.

Furthermore, by depolymerizing the recycled polyester raw material in the presence of ethylene terephthalate oligomer, ethylene glycol and phosphorus compound, the copolymerization component is present as compared with the case where the depolymerization is performed using only the recycled polyester raw material. Therefore, it becomes possible to proceed the depolymerization reaction at a low temperature. This is a great advantage when implemented on an industrial basis.

In the production method 1 of the present invention, it is desirable that the recycled polyester raw material is not decomposed into monomers but is decomposed into oligomers having a repeating unit of about 5 to 20 by the above depolymerization reaction. By controlling the depolymerization reaction in this way, not only various inorganic substances but also foreign substances derived from non-polyester resin can be efficiently deposited, and as a result, more foreign substances can be removed.

When the molar ratio of the total glycol component / total acid component in the depolymerization reaction is out of the above range, the obtained regenerated polyester resin has at least one of the carboxyl terminal group concentration and the diethylene glycol content specified in the present invention. Will not be satisfied, and the average boosting speed will be high. This is because when the molar ratio of the total glycol component / total acid component in the depolymerization reaction is out of the above range, foreign substances derived from various inorganic substances and non-polyester resins are not efficiently precipitated (2). In the step (3), these foreign substances cannot be completely filtered, and the foreign substances are precipitated after the polycondensation reaction in the step (3), resulting in a regenerated polyester resin having a high average step-up rate.

The reactor used in the production method 1 of the present invention has no particular problem in the capacity and the shape of the stirring blade in the generally used esterification reactor, but in order to efficiently proceed with the depolymerization reaction, ethylene glycol is used. It is preferable that the structure is provided with a distillation column that does not allow the reactor to accumulate outside the system.
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).

The reaction temperature at the time of depolymerization performed in the step (1) is preferably set in the range of 245 to 280 ° C. for the internal temperature of the reactor, and in particular, the internal temperature is set in the range of 255 to 280 ° C. It is more preferable to do so. 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 content of diethylene glycol and the concentration of carboxyl terminal groups are high. Too much. When the reaction temperature exceeds 280 ° C., the content of diethylene glycol and the concentration of carboxyl terminal groups in the obtained regenerated polyester resin become too high.
The reaction time for depolymerization (reaction time after the completion of charging of the recycled polyester raw material) is preferably 4 hours or less, and is within 2 hours from the viewpoint of suppressing the by-product amount of diethylene glycol and suppressing the deterioration of the color tone of the polyester. It is more preferable to do so.

In the step (2), the reaction product containing 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 foreign substances. As described above, by carrying out the depolymerization reaction under the conditions of the step (1), not only various inorganic substances but also foreign substances derived from non-polyester resin are efficiently deposited. Therefore, a filter having a filtration particle size of 10 to 25 μm is efficiently deposited. By passing through the above, the precipitated foreign matter can be filtered to obtain a filtrate having a small amount of foreign matter mixed.

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 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 and 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 deteriorates in operability.

Further, the filter that can be used in the step (2) of the present invention is a general one and has no particular problem, but examples thereof include a screen changer type filter, a leaf disc filter, and a candle type sintered filter.

Then, in the production method 1 of the present invention, the polymerization catalyst as described above is added to the filtrate obtained through the above step (2), and the polycondensation reaction is carried out at a temperature of 250 ° C. or higher and a reduced pressure of 1.0 hPa or lower. I do.

Then, in the polycondensation reaction tank, the polycondensation reaction is carried out under a reduced pressure of 250 ° C. or higher and 1.0 hPa or lower. If the polycondensation reaction temperature is less than 250 ° C. or the pressure during the polycondensation reaction exceeds 1.0 hPa, the polycondensation reaction time becomes long and the productivity becomes inferior.
The polycondensation reaction temperature is more preferably 270 ° C. or higher. However, if the polycondensation reaction temperature is too high, the polymer will be colored by thermal decomposition and the color tone will deteriorate, and the amount of terminal groups (COOH) will also increase due to thermal decomposition. Therefore, in the present invention, the upper limit of the polycondensation reaction temperature is reached. Is preferably 285 ° C. or lower. The ultimate viscosity of the regenerated polyester obtained here is preferably 0.44 to 0.80.

[Manufacturing method 2]
Next, the manufacturing method 2 described above will be described. The production method 2 is a method of blending the phosphorus compound (Y) after obtaining the recycled polyester resin. At this time, the following methods (a) and (b) can be adopted.
(B) Method of directly blending a phosphorus compound with a recycled polyester resin (b) Method of blending a polyester resin (master resin) containing a high concentration of a phosphorus compound with a recycled polyester resin The recycled polyester resin used in the manufacturing method 2 is In order to satisfy the characteristic values of the resin of the present invention, a) a component derived from at least one recycled polyester raw material of a) used polyester product and b) an unadopted polyester resin generated in the process of manufacturing the polyester product is used. When the total amount of all glycol components in the recycled polyester resin is 100 mol%, ethylene glycol is 80 mol% or more, diethylene glycol is 4 mol% or less, and the carboxyl terminal group concentration is 40 equivalents / t or less. It is preferable that the average step-up speed is 0.6 MPa / h or less. As such a recycled polyester resin, it is preferable to use the recycled polyester resin described in Japanese Patent Application No. 2020-059233, and it is preferable that the recycled polyester resin is obtained by the method for producing a recycled polyester resin described in the same item.

Further, in the production method (b), it is preferable to use the recycled polyester resin described in Japanese Patent Application No. 2020-059233 described above in consideration of the global environment as the polyester resin used for the master resin.

In both the manufacturing methods of (a) and (b), the recycled polyester resin obtained by the manufacturing method of the recycled polyester resin described in Japanese Patent Application No. 2020-059233 uses, for example, a screw type extruder in the recycled polyester resin. And a batch blending method in which a phosphorus compound or a master resin containing a phosphorus compound is added at the same time and melted / kneaded to pelletize, or a recycled polyester resin is melted / kneaded and then phosphoric acid is supplied from another supply port of the extruder. A split blending method can be adopted in which a master resin containing a compound or a phosphorus compound is supplied, melted and kneaded, and pelletized.

The resin of the present invention can obtain molded products (blow molded products, injection molded products, sheets, films, etc.) by adopting blow molding, injection molding, stretching methods, etc., and fibers can be obtained by melt spinning. Can be done.

In the case of a molded product, by containing 0.1 to 1.0% by mass of a hindered phenolic antioxidant, it is possible to prevent a decrease in the ultimate viscosity and a deterioration in color tone after molding.

In the case of a fiber containing the resin of the present invention, for example, the fiber can be manufactured by 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 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.

Further, in the production of fibers, it is generally more difficult to produce multifilaments, but in the fiber of the present invention, for example, the single yarn fineness is 0.3 to 30 decitex, the number of single yarns is 2 to 300, and the total fineness is 5. It can be a multifilament having characteristic values of ~ 350, strength 1-5 cN / decitex, and elongation 10-400%.
As described above, the resin of the present invention is excellent in thermal stability because the content of diethylene glycol and the concentration of the carboxyl-terminal group are not more than a specific amount. Therefore, when the long fibers as described above are obtained, thickness unevenness and the like are less likely to occur, and fibers having a high degree of uniformity can be obtained with good operability. Further, as described above, the resin of the present invention has an average step-up speed of 0.6 MPa / h or less and a small amount of foreign matter mixed therein. As foreign substances existing in the resin, inorganic substances and foreign substances derived from non-polyester resin are assumed, but due to the small amount of these foreign substances, the single yarn fineness is 1.0 decitex or less, especially 0.6 decitex or less. Can be obtained with good operability.

When the fiber of the present invention is a staple fiber, for example, a fiber having a single yarn fineness of 0.5 to 25.0 decitex, a strength of 0.1 to 6.0 cN / decitex, and an elongation of 20 to 600% can be obtained. .. As described above, the resin of the present invention is excellent in thermal stability because the content of diethylene glycol and the concentration of the carboxyl-terminal group are not more than a specific amount. Therefore, when the staple fibers as described above are obtained, even if the single yarn fineness is small, the single yarn fusion in the spinning and drawing steps is suppressed, the single yarn fineness is less likely to vary, and the staple is balanced. High degree of fiber can be obtained with good operability.
The non-woven fabric obtained by using short fibers having a small variation in single yarn fineness and a high degree of uniformity has a uniform distribution of the constituent short fibers in both the dry type and the wet non-woven fabric, and has high quality without spots. It becomes a thing.

Next, the present invention will be specifically described with reference to Examples. The measurement and evaluation methods for various characteristic values in the examples are as follows.
(A) Extreme Viscosity The obtained recycled polyester resin is used and measured at a temperature of 20 ° C. using an equal mass mixture of phenol and ethane tetrachloride as a solvent.
(B) Composition of polyester resin and content of phosphorus atom The obtained polyester resin was dissolved in a mixed solvent having a volume ratio of deuterated trifluoroacetic acid and deuterated chloroform of 1/11, and manufactured by JEOL Ltd. 1H-NMR was measured with a JNM-ECZ400R / S1 type NMR 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 group 0.1 g of the obtained regenerated polyester resin is dissolved in 10 ml of benzyl alcohol, 10 ml of chloroform is added to this solution, and then titrated with a 1/10 specified potassium hydroxide benzyl alcohol solution to obtain the determination. rice field.

(D) Average boosting speed measured by a booster tester The obtained recycled polyester resin is melted at 300 ° C. with an extruder, and a stainless steel plain weave filter (nominal size mesh:) is used as a filter at the tip of the extruder. 1400 mesh, weave: plain weave, vertical mesh: 165 mesh, horizontal mesh: 1400 mesh, vertical wire diameter: 0.07 mm, horizontal wire diameter: 0.04 mm, filtration grain size: 12 μm, viscous resistance coefficient (m-1) : 2.60 x 107, inertial resistance coefficient: 5.14 x 10, manufactured by Kamijo Seiki Co., Ltd., and a reinforcing material (stainless plain weave wire mesh (nominal size mesh: 40 mesh, woven)) on the back surface (downstream side). 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 by a pressure tester; "MES-Y44D type" manufactured by Asahi Gauge. Measure 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 passing through the filter). The minimum value of the pressure during the minute is taken as the initial pressure)) and the final pressure value (MPa) after 12 hours have passed, and the average boosting speed was calculated by the following formula.
Average boost rate (MPa / h) = (final pressure value-initial pressure value) / 12

(E) Melting point, glass transition temperature The obtained recycled polyester resin is heated (lowered) in a temperature range of 25 ° C to 280 ° C in a nitrogen stream using a differential scanning calorimeter (Diamond DSC) manufactured by PerkinElmer. The measurement was performed at a rate of 20 ° C./min and a sample volume of 8 mg.
(F) Operability of fiber production (cutting thread)
The operability was evaluated by the number of yarn breaks in the melt spinning process. A pass (◯) was given when the number of yarn breaks per ton of spinning amount was less than 3, and a fail (x) was given when the number of breaks was 3 or more.
(G) Single fiber fineness Measured by JIS L1015 8.5.1 B method.
(H) Texture of non-woven fabric The texture of the obtained non-woven fabric was visually evaluated in the following two stages.
◯: The distribution of constituent fibers is uniform, and there are very few spots.
X: The distribution of constituent fibers is uneven, and spots are conspicuous.
(I) Flame retardancy of non-woven fabric The non-woven fabric obtained in (h) was evaluated for flame retardancy by the critical oxygen concentration index (LOI) according to JIS K7201 A2. The LOI value is preferably 26% or more.

Example 1
[Recycled polyester resin]
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 under the conditions of 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.
46 parts by mass of the ethylene terephthalate oligomer was charged into the esterification reactor, and then 5.3 parts by mass of the phosphorus compound and 2.7 parts by mass of the phosphorus compound represented by the structural formula (a) and ethylene glycol (EG) were added. And the mixture E was obtained. Then, 46 parts by mass of a recycled polyester raw material (a pellet of polyester waste generated in the process of producing the polyester resin) was quantitatively charged 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 1.13. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 260 ° C.
Then, the obtained depolymerized polymer 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. Add 2.0 × 10 ^-4 mol and titanium oxide to 0.37% by mass with respect to 1 mol of the acid component of the polyester resin that can obtain antimony trioxide as a catalyst, and reduce the pressure of the PC can 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 polyester resin having an ultimate viscosity of 0.64.
[Manufacturing of fiber]
Using the obtained polyester resin, melt spinning was performed at a discharge rate of 312 g / min, a spinning temperature of 297 ° C., and a spinning speed of 1176 m / min using a spinneret having a hole number of 2160 H and a hole diameter of 0.16 mm. The number of yarn breaks during melt spinning was 1.5 times / ton. The obtained undrawn yarn was converged to obtain a tow of 50 ktex, and the yarn was drawn under the conditions of a drawing temperature of 70 ° C. and a drawing ratio of 3.2 times. After stretching, heat is set in a heat drum having a temperature of 199 ° C., and then an oil agent containing lauryl phosphate potassium salt as a main component is applied to the tow by a spray method, and the tow is heated by a heating roller at 170 ° C. , Heated with steam, introduced into a push-in crimper, and crimped. Then, the tow was cooled on a cooling conveyor without heat treatment in a dryer and cut into 32 mm to obtain staple fibers.
[Manufacturing of non-woven fabric]
The obtained short fibers are used as the main fibers, and the core-sheath type heat-fused fibers manufactured by Unitica (the core is polyethylene terephthalate and the sheath is a short fiber composed of a copolymerized polyester having a melting point of 110 ° C.) are used as the binder fibers. A single fiber fineness of 2.2 dtex and a fiber length of 51 mm) was used. The mass ratio of the main fiber / binder fiber was set to 80/20, a card web (meshing 100 g / m ² ) was prepared, and heat treatment was performed with a hot air dryer under the conditions of a temperature of 150 ° C., an air volume of 38 m ² / min, and a treatment time of 1 minute. To prepare a non-woven fabric having a texture of 100 g / m ² .

Examples 2-8, Comparative Examples 1-9
[Recycled polyester resin]
The same as in Example 1 except that the amount of ethylene terephthalate oligomer, ethylene glycol, phosphorus compound and recycled polyester raw material added during the depolymerization reaction, G / A and heat treatment temperature were changed to those shown in Table 1. A depolymerization reaction was carried out.
Further, a 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 recovering the filtrate and the heat treatment temperature in the polymerization reaction step were changed to those shown in Table 1.
[Manufacturing of fiber]
Using the obtained polyester resins (Examples 2 to 8 and Comparative Examples 1 to 9), short fibers were produced in the same manner as in Example 1.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 1.

Table 1 shows the operability and characteristic values of the polyester resins and staple fibers obtained in Examples 1 to 8 and Comparative Examples 1 to 9, and the evaluation of the nonwoven fabric.

Example 9
[Recycled polyester resin]
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 under the conditions of 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.
51.3 parts by mass of the ethylene terephthalate oligomer was charged into the esterification reactor, and then 2.7 parts by mass of ethylene glycol (EG) was added to obtain a mixture E. Then, 46 parts by mass of a recycled polyester raw material (a pellet of polyester waste generated in the process of producing the polyester resin) was quantitatively charged over about 2 hours via a rotary valve.
At this time, the recycled polyester raw material was added so that the molar ratio (G / A) of the total glycol component / total acid component was 1.16. Then, the depolymerization reaction was carried out for 1 hour under the heat treatment conditions of 260 ° C.
Then, the obtained depolymerized polymer 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. Add 2.0 × 10 ^-4 mol to 1 mol of the acid component of the polyester resin that can obtain antimony trioxide as a catalyst, reduce the pressure of the PC can, and after 60 minutes, the final pressure is 0.5 hPa and the temperature is 275 ° C. The polycondensation reaction was carried out for 4 hours to obtain a polyester resin (A) having an ultimate viscosity of 0.64.
Next, the temperature of the polyester resin (A) and the phosphorus compound was 290 ° C. so that the phosphorus compound represented by the structural formula (a) had a volume of 5.3 parts by mass with respect to 100 parts by mass of the obtained polyester resin (A). Was put into the extruder of the above to obtain a polyester resin having an ultimate viscosity of 0.62.
[Manufacturing of fiber]
Using the obtained polyester resin, staple fibers were produced in the same manner as in Example 1.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 1.

Examples 10 and 11, Comparative Examples 10 and 11
[Recycled polyester resin]
A polyester resin was produced in the same manner as in Example 9 except that the amount of the phosphorus compound added was changed to that shown in Table 2.
[Manufacturing of fiber]
Using the obtained polyester resin (Examples 10 and 11, Comparative Examples 10 and 11), short fibers were produced in the same manner as in Example 9.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 9.

Example 12
[Recycled polyester resin]
70 parts by mass of the polyester resin (A) obtained in Example 9 and 30 parts by mass of the phosphorus compound represented by the structural formula (a) are put into an extruder having a temperature of 290 ° C., and the polyester resin has a phosphorus compound of 30% by mass. (B) was obtained.
Subsequently, the polyester resin (A) was charged with 90 parts by mass and the polyester resin (B) with 10 parts by mass in an extruder at a temperature of 290 ° C. to obtain a polyester resin having an ultimate viscosity of 0.62.
[Manufacturing of fiber]
Using the obtained polyester resin, staple fibers were produced in the same manner as in Example 1.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 1.

Examples 13, 14, Comparative Examples 12, 13
[Recycled polyester resin]
A polyester resin was produced in the same manner as in Example 12 except that the blending ratios of the polyester resin (A) and the polyester resin (B) were changed to those shown in Table 3.
[Manufacturing of fiber]
Using the obtained polyester resin (Examples 13 and 14, Comparative Examples 12 and 13), short fibers were produced in the same manner as in Example 12.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 12.

Example 15
[Recycled polyester resin]
In Example 12, when the polyester resin (B) was obtained, the virgin polyester resin [polyethylene terephthalate (MA-6101-3 manufactured by Unitica)] was used instead of the polyester resin (A). Similarly, a polyester resin having an ultimate viscosity of 0.62 was obtained.
[Manufacturing of fiber]
Using the obtained polyester resin, staple fibers were produced in the same manner as in Example 12.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 12.

Example 16
[Recycled polyester resin]
Using the polyester resin (A) obtained in the same manner as in Example 9, a phosphinic acid metal salt (“Exolit OP950” manufactured by Clariant) was used as a phosphorus compound, and 100 parts by mass of the obtained polyester resin (A) was used. On the other hand, the polyester resin (A) and the phosphorus compound were put into an extruder at a temperature of 290 ° C. so that the amount of the phosphorus compound was 3.0 parts by mass to obtain a polyester resin having an ultimate viscosity of 0.62.
[Manufacturing of fiber]
Using the obtained polyester resin, staple fibers were produced in the same manner as in Example 1.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 1.

Example 17
[Recycled polyester resin]
Using the polyester resin (A) obtained in the same manner as in Example 9, a phosphinic acid metal salt (“Exolit OP950” manufactured by Clariant) was used as a phosphorus compound, and 100 parts by mass of the obtained polyester resin (A) was used. On the other hand, the polyester resin (A) and the phosphorus compound were put into an extruder at a temperature of 290 ° C. so that the phosphorus compound was 9.0 parts by mass to obtain a polyester resin having an ultimate viscosity of 0.61.
[Manufacturing of fiber]
Using the obtained polyester resin, staple fibers were produced in the same manner as in Example 1.
[Manufacturing of non-woven fabric]
Using the obtained staple fibers, a nonwoven fabric was produced in the same manner as in Example 1.

Table 2 shows the operability and characteristic values of the polyester resins and staple fibers obtained in Examples 9 to 11, 16 and 17, and Comparative Examples 10 to 11, and the evaluation of the nonwoven fabric.

Table 3 shows the operability and characteristic values of the polyester resins and staple fibers obtained in Examples 12 to 15 and Comparative Examples 12 to 13, and the evaluation of the nonwoven fabric.

As is clear from Tables 1 to 3, the recycled polyester resins obtained in Examples 1 to 17 have a phosphorus atom content, a carboxyl terminal group concentration, a diethylene glycol content, and an average step-up rate within the range specified in the present invention. It was inside. Therefore, it was possible to obtain fibers having excellent operability and flame retardancy when obtaining short fibers.

On the other hand, in Comparative Example 1, since the content of the phosphorus atom was as low as 740 mass ppm, the flame retardancy of the obtained fiber was low.
In Comparative Example 2, since the reaction temperature at the time of depolymerization was as high as 285 ° C., the content of diethylene glycol and the concentration of the carboxyl terminal group were high. Therefore, thermal decomposition occurs when the fiber is used, the operability is deteriorated, the heat shrinkage rate of the obtained fiber is high, and the texture of the non-woven fabric is poor.
In Comparative Example 3, since the candle filter provided between the ES can and the PC can was as low as 5 μm, clogging occurred in the filtration step and the polyester resin could not be obtained.
In Comparative Example 4, since the filtration particle size of the candle filter provided between the ES can and the PC can was as high as 30 μm, the amount of foreign matter mixed was large and the average step-up speed was high. Therefore, when the fiber is used, the pressure applied to the nozzle pack and the frequent occurrence of thread breakage deteriorate the operability and the texture of the non-woven fabric is also poor.

In Comparative Example 5, since the G / A at the time of depolymerization was as low as 1.05, the depolymerization was not sufficiently performed and the removal of foreign substances was insufficient, so that the average step-up rate was high. In addition, the concentration of the carboxyl-terminal group was high, thermal decomposition occurred when the fiber was made, the operability was deteriorated, and the texture of the non-woven fabric was also poor.
In Comparative Example 6, since the content of the phosphorus atom was as high as 10980 mass ppm, the resin had low crystallinity, fusion occurred during drying, and the fiber process could not proceed.
In Comparative Example 7, since the G / A at the time of depolymerization was as high as 1.34, the content of diethylene glycol was high. Therefore, the crystallinity and thermal stability are low, the operability is deteriorated when the fiber is used, the heat shrinkage rate of the obtained fiber is high, and the texture of the non-woven fabric is poor.

In Comparative Example 8, since the reaction temperature at the time of depolymerization was as low as 240 ° C., the polyester oligomer was solidified during the depolymerization reaction, and the polyester resin could not be obtained.
In Comparative Example 9, since the polycondensation temperature was as low as 250 ° C., the polycondensation reaction did not proceed and the polyester resin could not be obtained.
In Comparative Example 10, since the content of the phosphorus atom was as low as 730 mass ppm, the flame retardancy of the obtained fiber was low.

In Comparative Example 11, since the content of the phosphorus atom was as high as 11060 mass ppm, the resin had low crystallinity, fusion occurred during drying, and the fiber process could not proceed.
In Comparative Example 12, since the content of the phosphorus atom was as low as 630 mass ppm, the flame retardancy of the obtained fiber was low.
In Comparative Example 13, since the content of the phosphorus atom was as high as 11040 mass ppm, the resin had low crystallinity, fusion occurred during drying, and the fiber process could not proceed.

Claims (4)

A recycled 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) It contains a phosphorus compound, and the content of phosphorus atoms in the polyester resin is 1000 to 10000 mass ppm.
(2) When the total amount of all glycol components is 100 mol%, ethylene glycol is 80 mol% or more and diethylene glycol is 4 mol% or less.
(3) The carboxyl terminal group concentration is 40 equivalents / t or less, and the concentration is 40 equivalents / t or less.
(4) The average boosting speed is 0.6 MPa / h or less (however, the average boosted speed is a value calculated by the following procedure: using a booster 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 grain 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. When the pressure value at the time is "initial pressure value (MPa)" and the pressure value at the time of continuous extrusion for 12 hours is "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 that. A molded product containing the recycled polyester resin according to claim 1. The fiber 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) used polyester product and b) an unadopted polyester resin generated in the process of manufacturing the polyester product.
(1) A recycled polyester raw material is added to a mixture containing an ethylene terephthalate oligomer, ethylene glycol and a phosphorus compound so that the molar ratio of the total glycol component / total acid component is 1.06 to 1.20, and 245 to 280. A step of obtaining a reaction product containing a depolymerized product by performing depolymerization under heat treatment conditions at ° C.
(2) A step of passing the reaction product through a filter having a filtration particle size of 10 to 25 μm and collecting the filtrate.
(3) A step of adding a polymerization catalyst to the filtrate and performing a polycondensation reaction of the depolymerized product under a reduced pressure of 250 ° C. or higher and 1.0 hPa or lower.
A method for producing a recycled polyester resin, which comprises.