JP2005105091A - Polyalkylene terephthalate waste-treated mass and treating method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain terephthalic acid and an alkylene glycol in high purities as split products using a polyalkylene terephthalate-treated product as feedstock which is obtained by efficiently removing metal(s) from polyalkylene terephthalate wastes containing the metal(s) derived from esterification and/or polycondensation catalyst(s). <P>SOLUTION: A treating method is provided, comprising retrieving polyalkylene terephthalate-based wastes generated from commercial polyalkylene terephthalate-based products and/or in the process of producing the products and recovering effective ingredients. Specifically, this method comprises the following procedure: The polyalkylene terephthalate wastes are charged into an alkylene glycol followed by agitation under heating at 100-180°C to selectively dissolve into the alkylene glycol metal compound(s) derived from the esterification and/or polycondensation catalyst(s) contained in the system to remove the metal compound(s). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recycling active ingredients from polyalkylene terephthalate waste, and more particularly to a method for recycling polyalkylene terephthalate that can be carried out semipermanently by avoiding quality degradation due to the implementation of recycling.

The consumption of polyalkylene terephthalate products (bottle containers, films, fibers, etc.) has been increasing year by year, and in particular, the increase in consumption of polyethylene terephthalate bottles (PET bottles) is significant. 220,000 tons, 330,000 tons were consumed in 1998, and in 2001 the consumption exceeded 400,000 tons. In the future, the consumption of polyethylene terephthalate products is expected to increase year by year, and improving the collection rate and recycling rate of used polyethylene terephthalate products has become an essential proposition on a global scale.
Recently, the law requires the separate collection and recycling of used PET bottles, and the government and the private sector are working together to collect and recycle used PET bottles. The recovery rate increases year by year and exceeds 40% in 2001. However, at present, the use of recycled products is limited, and the expansion of the use of recycled products has become an issue as the recovery rate is improved.

Conventionally, collected PET bottles are sorted, volume-reduced and compressed by municipalities into PET bottle veils (for example, about 40 × 40 × 60 cm) and delivered to re-commercializers. The re-commercializing company unraveles this, separates foreign matters such as metal and PVC bottles, and after washing, further separates the colored bottles, and then pulverizes them to separate labels, aluminum, and the like. Furthermore, after washing, plastics other than polyalkylene terephthalate (polyethylene, polystyrene, etc.) are separated, dehydrated and dried, and then metal is further separated by magnetic force to form flakes or pellets.
The flakes are sent to a user, who uses the flakes or pellets as raw materials to make products other than PET bottles, such as carpets, packaging films such as eggs, and short fibers.

In recent years, as a method for recovering a raw material for polymerization of PET bottles again from a PET bottle, various methods for chemically decomposing polyalkylene terephthalate to recover oligomers or monomers and polymerizing polyalkylene terephthalate again have been developed. For example, the method disclosed in JP 2001-335518 is a method of hydrolyzing polyethylene terephthalate into raw material components. In this method, terephthalic acid, which is a raw material of polyethylene terephthalate, and / or a metal such as a catalyst used for esterification of dimethyl terephthalate and ethylene glycol, and / or a polyalkylene terephthalate added during polycondensation and derived from the catalyst remaining in the resin Since such metals cannot be completely removed, the obtained terephthalic acid cannot be used as it is as a raw material for high-quality fibers, films, beverage bottles and the like.
JP 2001-335518 A

  The problem to be solved is to efficiently remove the metal from the polyalkylene terephthalate product and / or waste containing metal such as derived from the esterification and / or polycondensation catalyst during the production of the polyalkylene terephthalate. This is the point that a decomposition product terephthalic acid and alkylene glycol are obtained with high purity using an alkylene terephthalate-treated body as a raw material.

As a result of intensive studies in view of the above-described conventional technology, the present inventors have efficiently dissolved and separated the metal compound contained by treating with alkylene glycol under low temperature conditions, and then depolymerized. The terephthalic acid obtained in this way was found to contain substantially no metal derived from polyalkylene terephthalate, and the target product could be efficiently recovered, thereby completing the present invention.
That is, in a method for purifying polyalkylene terephthalate, the polyalkylene terephthalate is characterized in that the amount of metal contained is reduced by stirring the polyalkylene terephthalate in an alkylene glycol at a temperature of 100 ° C. to 180 ° C. The alkylene glycol is preferably equal to the diol monomer component constituting the polyalkylene terephthalate.

  According to the method of the present invention, the polyalkylene terephthalate waste is treated with alkylene glycol to selectively remove the metal such as catalyst derived during the production of polyalkylene terephthalate contained in the polyalkylene terephthalate. By performing a depolymerization reaction using the obtained polyalkylene terephthalate-treated product as a raw material, a high-purity raw material monomer can be recovered. Therefore, since the raw material monomer recovered from polyalkylene terephthalate waste can be used as it is for polyalkylene terephthalate polymerization, it produces polyalkylene terephthalate fibers with good color tone, films with good hue and transparency, and hollow molded articles. become able to. As a result, good recycling of polyalkylene terephthalate waste can be achieved, resource saving can be achieved, and environmental conservation can be contributed.

Hereinafter, the present invention will be described in detail with specific examples. In the present invention, the polyalkylene terephthalate-treated body refers to a treated body from which the catalyst metal (hereinafter sometimes simply referred to as catalyst metal) derived from esterification and / or polycondensation added during the production of polyalkylene terephthalate is removed. That is, in a method for purifying polyalkylene terephthalate, the amount of metal contained is reduced by heating and stirring polyalkylene terephthalate in alkylene glycol at a temperature of 100 ° C. to 180 ° C., that is, metal in polyalkylene terephthalate waste. When the amount C _{R is} the amount of metal C _T in the polyalkylene terephthalate-treated body after the alkylene glycol treatment, it is characterized by following the formula C _T / C _R <1. Preferably, C _T / C _R <0.8, more preferably C _T / C _R <0.6. The alkylene glycol is preferably equal to the diol monomer component constituting the polyalkylene terephthalate.

When the molecular weight of the polyester mainly composed of polyalkylene terephthalate is M _R before heating and stirring and M _T after heating and stirring, M _T / M _R <1 is satisfied. Here, the intrinsic viscosity as an index was used as the molecular weight. Intrinsic viscosity weighs 1.2 g of polyester, prepares 0.5 g / dl sample solution using phenol / 1,1,2,2-tetrachloroethane mixed solvent (50/50 weight ratio), and measures at 25 ° C. Calculated from the solution viscosity. The number average molecular weight and the weight average molecular weight measured by other known molecular weight measurement methods such as gel permeation chromatography may be used, and both satisfy M _T / M _R <1.

The metal compound derived from the esterification and / or polycondensation catalyst is Al, Ba, Ca, Cd, Ce, Co, Ge, K, Li, Mg, Mn, Na, P, Pd, Sb, Sn, Ti, Zn. One of the above or a combination thereof.
Deriving from the esterification and / or polycondensation catalyst includes mixing as a filler, a flame retardant, a dye, a pigment, a stabilizer and the like as a metal mixing means other than the catalyst during polymerization and / or molding.

The polyalkylene terephthalate treatment can be performed in any of batch, semi-continuous and continuous processes.
The amount of alkylene glycol relative to polyalkylene terephthalate is preferably 1 to 100 times by weight, more preferably 4 to 40 times by weight. The residence time is preferably maintained for 10 minutes to 2 hours. Next, in order to recover the polyalkylene terephthalate from the alkylene glycol, a solid-liquid separator can be applied, but it may be separated by other conventional techniques. At this time, it is preferable to wash the polyalkylene terephthalate with further purified alkylene glycol after separation so that the dissolved catalyst metal does not remain attached to the polyalkylene terephthalate-treated body. Furthermore, you may wash | clean with water, such as distilled water and ion-exchange water.

  The polyalkylene terephthalate-treated product is depolymerized, and the depolymerization method may be any of the following methods, and when the polyalkylene terephthalate-treated product is used as a raw material for any process, untreated polyalkylene terephthalate is discarded. It is more effective than using things. That is, bis (2-hydroxyethyl) terephthalate by hydrolysis reaction with high pressure and high temperature water as disclosed in JP-A No. 2001-335518, or by depolymerization with alkylene glycol as disclosed in JP-A No. 2002-282601. Or a process for obtaining dimethyl terephthalate by transesterification with methanol in addition to depolymerization with alkylene glycol, as disclosed in JP-A No. 2002-167469, or methanol as disclosed in JP-A No. 2002-338507 The process of directly obtaining dimethyl terephthalate.

The hydrolysis process is shown as an example below. In this case, it is melted in a water-rich state to the extent that it has been centrifugally dehydrated and simultaneously hydrolyzed to form a polyalkylene terephthalate melt having a low degree of polymerization, and this polyalkylene terephthalate melt is mixed with water under high pressure and high temperature for hydrolysis. And effective.
A flowchart is shown in FIG. 1 as one example of the hydrolysis step. The polyalkylene terephthalate-treated body treated in the EG treatment tank 1 is removed from the excess EG by the solid-liquid separator 2 and then melted at 260 to 300 ° C. by the supply device 3. Supplied to. The pressure is increased to 5 to 30 MPa, preferably 10 to 30 MPa, and supplied.
At the inlet of the reactor 5, high-temperature and high-pressure water that has been heated and pressurized from the water supply device 8, that is, water having a temperature of 200 to 450 ° C., preferably 300 to 450 ° C., and a pressure of 5 to 40 MPa, preferably 10 to 30 MPa. The molten polyester is mixed and supplied to the reactor 5.

The weight ratio of the molten polyester to the water supplied here is adjusted to 2 to 10%, preferably 3 to 5%, and mixed and supplied at the reactor inlet. Moreover, it is preferable that the temperature of water is higher than polyester and / or reactor internal temperature. That is, the molten polyester is heated to near the reaction temperature by obtaining the heat energy of the heated water.
The water supplied to the reactor is preferably degassed dissolved oxygen. That is, the dissolved oxidation acts as an oxidant in the hydrolysis step described later and not only accelerates the hydrolysis of the polyester, but the organic matter may be oxidized and cause impurities.

The reactor 5 contains high-temperature high-pressure water and molten polyester to form a supercritical water region or a subcritical water region, and the polyester is hydrolyzed. The reactor 5 may be a known vertical tube reactor called a vessel type or a tubular reactor called a pipe type.
The processing fluid reacted in the reactor 5 contains supercritical water or subcritical water, decomposition products such as terephthalic acid, ethylene glycol, and decomposition byproducts, as well as inorganic impurities such as metals derived from the catalyst. Contains.

It is desirable to remove insoluble matter using a filter at the outlet of the reactor.
The processing fluid that has passed through the filter is cooled by a heat exchanger and further depressurized by a pressure reducing valve. Solid terephthalic acid precipitates at room temperature from the cooled and decompressed processing fluid. In order to collect the precipitated terephthalic acid, solid-liquid separation is performed using a separation device 5 such as a centrifugal separator, a plate frame type pressure filter, a leaf filter, or a cylindrical continuous vacuum filter. The terephthalic acid recovered as a solid content is sent directly to the next purification step or after recovery to the recovery tank.

On the other hand, the liquid component separated by the separator 6 is separated into water containing low-boiling organic substances and ethylene glycol containing heavy components by a normal distillation apparatus 9, and the water is further purified by a known purification method. It is supplied again to the water supply device 8 (not shown).
Similarly, ethylene glycol containing heavy components is also purified by the distillation apparatus 3 to obtain ethylene glycol. The ethylene glycol can be used again for EG treatment, can be used for polyester production, and can be used as a raw material for antifreeze. Further, the heavy component or ethylene glycol containing the heavy component can be used as it is as a fuel for a boiler or the like.

The obtained terephthalic acid may be purified as follows or may be used as a polycondensation raw material as it is.
The terephthalic acid separated by the solid-liquid separation device 5 includes an ester compound in the middle of decomposition such as mono (2-hydroxyethyl) terephthalate and / or bis (2-hydroxyethyl) terephthalate, and excess benzoic acid. Decomposition products and / or aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid, cyclohexanedicarboxylic acid and functional derivatives thereof, cyclohexane It may contain aliphatic dicarboxylic acids such as dicarboxylic acids and functional derivatives thereof. Furthermore, a metal compound such as a transesterification catalyst, an esterification catalyst and / or a polycondensation catalyst (hereinafter sometimes simply referred to as a catalyst) at the time of producing the polyester that has passed through the filter may be contained.

  The terephthalic acid containing these organic and / or inorganic impurities can be directly fed into a known terephthalic acid production process. This makes it possible to re-purify the polyester monomer obtained from the waste polyester into a high-purity monomer from which polyester can be produced, without installing new equipment. The terephthalic acid production process is a process called SD method or Amoco method, and is a process for obtaining terephthalic acid by air oxidation of paraxylene in an acetic acid solvent as disclosed in Japanese Patent Publication No. 37-2666, for example. . In this process, the terephthalic acid discharged together with the solvent from the oxidation reactor is solid-liquid separated by a centrifugal separator and then reslurried again with an acetic acid solvent for washing. Terephthalic acid containing organic and / or inorganic impurities obtained by hydrolysis from the waste polyester of the present invention is added to the reslurry step.

In the reslurry step, the transesterification catalyst, esterification catalyst and / or polycondensation catalyst-derived metal contained in the terephthalic acid obtained by hydrolysis from the waste polyester of the present invention is dissolved and removed in acetic acid. Here, the temperature of the reslurry process is 30 to 200 ° C., preferably 50 to 120 ° C., and the concentration of terephthalic acid with respect to acetic acid is 10 to 60% by weight, preferably 20 to 50% by weight. An aqueous acetic acid solution containing 5 to 40% by weight of water is used.
Acetic acid containing a metal such as the ester exchange catalyst, esterification catalyst and / or polymerization catalyst can be supplied as it is to the paraxylene oxidation reactor.

The terephthalic acid from which the metal such as catalyst is removed is subjected to solid-liquid separation and drying according to a known facility, and is stored as crude terephthalic acid in a silo and then supplied to the purification step.
The crude terephthalic acid can be removed by hydrogenation of colored impurities as disclosed in, for example, British Patent No. 994769, and the purity can be improved by recrystallization as disclosed in, for example, British Patent No. 781936. Purification can be carried out by a known technique.

  Crude terephthalic acid is slurried with water and the terephthalic acid concentration is adjusted to 10 to 60% by weight, preferably 20 to 50% by weight. The temperature is increased and the pressure is increased until the terephthalic acid slurry is completely dissolved. The solubility of terephthalic acid is about 270 ° C. at 20% and about 300 ° C. at 50%. The dissolved aqueous terephthalic acid solution is hydrogenated with hydrogen in the presence of a known hydrogenation catalyst. For existing terephthalic acid production facilities, the main reaction is hydrogenation of 4-carboxybenzaldehyde to form water-soluble p-toluic acid, but in the terephthalic acid of the present invention, the coloring component derived from the conjugated double bond Removal is the objective. However, even for different purposes, it is possible to operate in exactly the same operating conditions as existing facilities, and there is no limitation by supplying terephthalic acid derived from waste polyester. Furthermore, in this invention, ester bodies in the middle of decomposition, such as mono (2-hydroxyethyl) terephthalate and / or bis (2-hydroxyethyl) terephthalate contained in the crude terephthalic acid obtained in the hydrolysis step, are subjected to high-temperature and high-pressure conditions. The effect of being hydrolyzed and improving the purity of terephthalic acid is also observed.

The aqueous terephthalic acid solution from the hydrogenation step is gradually reduced in pressure and reduced in temperature by several crystallization drums that are continuously connected in series. During this process, crystals of terephthalic acid grow gradually, and impurities derived from highly soluble organic substances are dissolved and separated from terephthalic acid, improving the purity of terephthalic acid.
Once purified terephthalic acid with high purity is obtained as described above, it is used as a raw material together with ethylene glycol in a known high-purity polyester polymer production facility.
By these operations, a high-purity polyester polymer equivalent to or higher than virgin can be obtained, and various polyester products can be produced in the same manner as virgin raw materials by known techniques.

  The method for producing the high-purity polymer is a known method, but the production of the polyalkylene terephthalate resin composition will be described below for reference. Generally, an aromatic dicarboxylic acid and an aliphatic diol are transesterified to form bis (2-hydroxyethyl) terephthalate and / or its oligomer, and then subjected to high-temperature decompression in the presence of a polycondensation catalyst and a stabilizer. A polyalkylene terephthalate resin composition is obtained by performing melt polycondensation below.

Examples of the aromatic dicarboxylic acid used in the present invention include phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4 ′ in addition to purified terephthalic acid obtained by hydrolysis from the waste polyester raw material. Aromatic dicarboxylic acids such as dicarboxylic acids and diphenoxyethanedicarboxylic acids can be used together.
Similarly, as the aliphatic diol, in addition to purified ethylene glycol obtained by hydrolysis from the waste polyester raw material, fats such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexanemethylene glycol, and dodecamethylene glycol are used. Group glycols can be used.

In addition to aromatic dicarboxylic acids, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid and decanedicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used as raw materials. In addition, alicyclic glycols such as cyclohexanedimethanol, aromatic diols such as bisphenol, hydroquinone, and 2,2-bis (4-β-hydroxyethoxyphenyl) propane can be used as raw materials.
Furthermore, in this invention, polyfunctional compounds, such as a trimesic acid, a trimethylol ethane, a trimethylol propane, a trimethylol methane, a pentaerythritol, can be used as a raw material.

(Esterification step) First, when producing polyester, an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof are esterified.
Specifically, a slurry containing an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic diol or an ester-forming derivative thereof is prepared. In such a slurry, 1.005 to 1.4 mol, preferably 1.01 to 1.3 mol of an aliphatic diol or an ester thereof is formed per mol of the aromatic dicarboxylic acid or an ester-forming derivative thereof. Sex derivatives. This slurry is continuously supplied to the esterification reaction step.

The esterification reaction is preferably carried out under conditions where ethylene glycol is refluxed using an apparatus in which two or more esterification reaction groups are connected in series, while removing water produced by the reaction from the system using a rectification column.
The esterification reaction step is usually performed in multiple stages, and the first stage esterification reaction usually has a reaction temperature of 240 to 270 ° C., preferably 245 to 265 ° C., and a pressure of 0.02 to 0.3 MPaG. The final esterification reaction is preferably carried out under conditions of 0.05 to 0.2 MPaG, and the reaction temperature is usually 250 to 280 ° C., preferably 255 to 275 ° C., and the pressure is 0 to 0. .15 MPaG, preferably 0 to 0.13 MPaG.

When the esterification reaction is carried out in two stages, the esterification reaction conditions of the first stage and the second stage are within the above ranges, respectively, and when carried out in three stages or more, the second stage The esterification reaction conditions up to one stage before the final stage may be any conditions between the reaction conditions of the first stage and the final stage.
For example, when the esterification reaction is carried out in three stages, the reaction temperature of the second stage esterification reaction is usually 245 to 275 ° C., preferably 250 to 270 ° C., and the pressure is usually 0 to 0.00. It may be 2 MPaG, preferably 0.02 to 0.15 MPaG.

Although the esterification reaction rate in each of these stages is not particularly limited, it is preferable that the degree of increase in the esterification reaction rate in each stage is smoothly distributed, and further in the esterification reaction product in the final stage. Usually, it is desirable to reach 90% or more, preferably 93% or more.
By this esterification step, an esterification reaction product (low-order condensate) of an aromatic dicarboxylic acid and an aliphatic diol is obtained, and the number-average molecular weight of this low-order condensate is about 500 to 5,000.

The low-order condensate obtained in the esterification step as described above is then supplied to the polycondensation (liquid phase polycondensation) step. (Liquid phase polycondensation step) In the liquid phase polycondensation step, in the presence of a known polycondensation catalyst, the low-order condensate obtained in the esterification step is subjected to a temperature equal to or higher than the melting point of the polyester under reduced pressure ( Usually, polycondensation is carried out by heating to 250 to 280 ° C. This polycondensation reaction is desirably carried out while distilling off unreacted aliphatic diol out of the reaction system.
As polycondensation catalysts, germanium compounds, antimony compounds, titanium compounds, cobalt compounds, tin compounds and the like are generally known.

  The polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. For example, when the polycondensation reaction is performed in a plurality of stages, the first stage polycondensation reaction has a reaction temperature of 250 to 290 ° C., preferably 260 to 280 ° C., and a pressure of 500 to 20 Torr, preferably 200 to The final polycondensation reaction is carried out under the conditions of 30 Torr and the reaction temperature is 265 to 300 ° C., preferably 270 to 295 ° C., and the pressure is 10 to 0.1 Torr, preferably 5 to 0.5 Torr. Done.

  When the polycondensation reaction is carried out in three or more stages, the polycondensation reaction between the second stage and the first stage before the last stage is performed between the reaction conditions of the first stage and the reaction conditions of the last stage. It is done on the condition between. For example, when the polycondensation process is performed in three stages, the second stage polycondensation reaction is usually performed at a reaction temperature of 260 to 295 ° C., preferably 270 to 285 ° C., and a pressure of 50 to 2 Torr, preferably It is carried out under conditions of 40 to 5 Torr.

  The polycondensation reaction is desirably performed in the presence of a stabilizer. Specific examples of the stabilizer include phosphate esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate; triphenyl phosphite, trisdodecyl phosphite, trisnonyl phenyl phosphite Phosphites such as: methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate, etc. It is done.

  The use ratio of the above catalyst is in the range of 2 to 1000 ppm, preferably 4 to 500 ppm as the weight of metal in the catalyst in all the polymerization raw materials, and the use ratio of the stabilizer is the weight of phosphorus atom in the stabilizer in all raw materials. Is usually in the range of 4 to 1000 ppm, preferably 4 to 500 ppm. In addition, the catalyst and the stabilizer can be supplied at any stage of the esterification reaction in addition to the preparation of the raw material slurry in the known technique. Further, it can be supplied at the initial stage of the polycondensation reaction step.

The intrinsic viscosity [IV] of the polyester obtained by the liquid phase polycondensation process as described above is 0.40 to 1.0 dl / g, preferably 0.50 to 0.90 dl / g. The intrinsic viscosity achieved in each stage excluding the final stage of the liquid phase polycondensation process is not particularly limited, but it is preferable that the degree of increase in intrinsic viscosity in each stage is smoothly distributed.
In this specification, the intrinsic viscosity [IV] is determined by measuring 1.2 g of polyester and 0.5 g / dl using a phenol / 1,1,2,2-tetrachloroethane mixed solvent (50/50 weight ratio). The sample solution was prepared and calculated from the solution viscosity measured at 25 ° C.

The polyester obtained in this polycondensation step is usually melt-extruded and formed into granules (chips). (Solid phase polycondensation step) The polyester obtained in this liquid phase polycondensation step can be further subjected to solid phase polycondensation if desired.
The granular polyester supplied to the solid phase polycondensation step may be supplied to the solid phase polycondensation step after preliminarily crystallizing by heating in advance to a temperature lower than the temperature in the case of performing solid phase polycondensation. .

  Such a precrystallization step can be performed by heating the granular polyester in a dry state to a temperature of usually 120 to 200 ° C., preferably 130 to 180 ° C. for 1 minute to 4 hours. Such pre-crystallization can also be performed by heating the granular polyester at a temperature of 120 to 200 ° C. for 1 minute or more in a steam atmosphere, a steam-containing inert gas atmosphere, or a steam-containing air atmosphere.

  The precrystallized polyester desirably has a crystallinity of 20 to 50%. Note that, by this precrystallization treatment, so-called polyester solid-phase polycondensation reaction does not proceed, and the intrinsic viscosity of the precrystallized polyester is almost the same as the intrinsic viscosity of the polyester after liquid-phase polycondensation, The difference between the intrinsic viscosity of the pre-crystallized polyester and the intrinsic viscosity of the polyester before the pre-crystallization is usually 0.06 dl / g or less.

The solid phase polycondensation step consists of at least one stage, the temperature is 190 to 230 ° C., preferably 195 to 225 ° C., and the pressure is 0.1 MPaG to 10 Torr, preferably normal pressure to 100 Torr. The reaction is performed under an inert gas atmosphere such as argon or carbon dioxide. Nitrogen gas is desirable as the inert gas used.
The granular polyester obtained through such a solid-phase polycondensation step may be subjected to water treatment, for example, by the method described in JP-B-7-64920. It is carried out by bringing it into contact with a steam-containing inert gas, steam-containing air or the like.

  The intrinsic viscosity of the granular polyester thus obtained is usually 0.60 to 1.00 dl / g, preferably 0.75 to 0.95 dl / g. The production process of the polyester including the esterification step and the polycondensation step as described above can be performed in any of a batch type, a semi-continuous type, and a continuous type.

  The polyester thus produced may contain conventionally known additives such as stabilizers, mold release agents, antistatic agents, dispersants, colorants such as dyes and pigments, etc. The additive may be added at any stage during the production of the polyester, or may be added by a master batch before molding.

  Polyester obtained by the present invention is made into various polyester film product groups by making polyester film in the film forming equipment, or polyester raw yarn or cotton in the yarn making equipment, such as textile garments, carpets, automotive interior materials, futons, flooring materials, etc. It can also be made into a product. Moreover, the said polymer can also be used as a raw material for PET bottles and engineering plastics by subjecting it to necessary treatment in a solid phase polymerization facility.

  According to the recycling method of the present invention, since the original polyester product group can be produced again from almost all polyester-containing waste, an almost complete “circulation type recycling system” can be realized. It is now possible to easily circulate from polyester bottles that contain fiber waste, including PET bottles, which is a major issue, to landfill and incinerate, etc. as general and industrial waste. There is no need. Therefore, it is an effective recycling method that can solve the waste treatment problem and achieve resource and energy savings.

  Hereinafter, the contents of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these. In this embodiment, PET bottle flakes are used as the starting material. Of course, a veil obtained by reducing and compressing a used PET bottle may be used as a starting material. This PET bottle veil is manufactured by a publicly known method currently employed by municipalities. Other polyester wastes can be used as starting materials.

In addition, each numerical value in an Example was calculated | required with the following method. In the examples, “parts” means “parts by weight” unless otherwise specified. (1) Intrinsic viscosity (hereinafter sometimes abbreviated as IV): A predetermined amount of a sample cut out from a chip and a molded body is weighed, and a phenol / 1,1,2,2-tetrachloroethane mixed solvent (50/50 weight) Ratio) was used to prepare a 0.5 g / dl sample solution, and the intrinsic viscosity (IV) was calculated from the solution viscosity measured at 25 ° C. (2) Metal analysis: The sample was decomposed with concentrated sulfuric acid and concentrated nitric acid, and then measured using high-frequency plasma emission analysis. (3) Terephthalic acid purity: 10 mg of terephthalic acid was dissolved in 10 ml of DMF, and high performance liquid chromatography (Nippon Waters Co., Ltd. 2690 Alliance system, column: Develosil ODS-HG-3 4.6 × 150 mm (Nomura Chemical Co., Ltd.) ), Solvent: 0.25% acetic acid aqueous solution / acetonitrile = 85/15, detector: UV 254 nm). (4) b value: The b value of the sample was measured from reflected light using a color meter SQ-300H manufactured by Nippon Denshoku Co., Ltd. (5) Haze: Using a haze meter NDH20D manufactured by Nippon Denshoku Co., Ltd., a method similar to ASTM D1003 was used to measure a 5 mm thick haze of a stepped square plate-like molded product as shown in FIG. .

Into a 100 ml flask, 180 parts of ethylene glycol was added, and further 20 parts of polyethylene terephthalate flake (manufactured by Yono PET Bottle Recycle Co., Ltd.) was added, and the temperature was increased while stirring. After heating up to 160 degreeC, it stirred for 30 minutes, keeping at 160 degreeC. Thereafter, it was filtered off with a glass filter, further washed with 100 parts of ethylene glycol, twice with 100 parts of distilled water, and filtered to obtain a polyethylene terephthalate-treated body.
Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

  The same operation was performed except that the heating temperature and the heating time were changed in Example 1. Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

  The same operation was performed except that the heating temperature and the heating time were changed in Example 1. Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

  The same operation was performed except that the heating temperature and the heating time were changed in Example 1. Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

  The same operation was performed except that the heating temperature and the heating time were changed in Example 1. Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

  The same operation was performed except that the heating temperature and the heating time were changed in Example 1. Table 1 shows the metal analysis results and intrinsic viscosity of the obtained polyethylene terephthalate-treated body.

The polyethylene terephthalate-treated product obtained in Example 1 was subjected to a hydrolysis reaction in the same experimental apparatus as shown in FIG. 2000 parts of the polyethylene terephthalate-treated body was continuously supplied from the receiving tank 1 to the polyethylene terephthalate dissolution tank 2. The polyethylene terephthalate dissolution tank was maintained at 260 ° C. to dissolve the polyethylene terephthalate. On the other hand, 6000 parts of water was continuously supplied from the water tank 4, the pressure was increased to 25 MPa, the temperature was increased to 380 ° C., and the mixture was mixed with molten polyethylene terephthalate at the reactor inlet, and then supplied to the reactor 3. The reactor 3 was maintained at a temperature of 350 ° C. and a pressure of 25 MPa, and the residence time was 18 minutes. The reaction product was continuously withdrawn from the top of the column, cooled and decompressed. A 7 μm filter was installed at the reactor outlet. The obtained product was separated into solid and liquid by filtration.
The obtained solid content had a terephthalic acid purity of 99.97%, and the residual metals all had a concentration of ≦ 0.05 ppm.
[Reference Example 1]

  Polyester was polymerized using purified terephthalic acid and ethylene glycol obtained as in Example 7. 13,000 parts of the terephthalic acid and 5340 parts of ethylene glycol were supplied to the esterification reaction layer at 100 ° C. and normal pressure. Next, the temperature was raised to 260 ° C., and the reaction was carried out for 340 minutes in a nitrogen atmosphere under a pressure of 0.1 MPaG. Water purified by the reaction was always distilled out of the system.

Next, 47.9 parts of germanium ethylene glycol solution (0.036 mol% with respect to terephthalic acid) as a catalyst and 2.2 parts of methyl acid phosphate (to terephthalic acid as a stabilizer) in the esterification reaction tank returned to normal pressure. Then, the total amount in the esterification tank was transferred to a polycondensation reaction tank at 260 ° C. in advance. The temperature was raised from 260 ° C. to 285 ° C. over 60 minutes, and the pressure was reduced from normal pressure to 2 torr.
Furthermore, after performing the reaction in a polycondensation reaction tank for 53 minutes, the reaction product was taken out in a strand form outside the polycondensation reaction tank, cooled by immersion in water, and cut into granules with a strand cutter to obtain polyethylene terephthalate. . This polyethylene terephthalate had an intrinsic viscosity of 0.542 dl / g and a germanium content of 65 ppm. The obtained polymer had a hue b value of -0.1.

Further, the polyethylene terephthalate obtained by liquid phase polymerization is transferred to a solid phase polymerization tower, crystallized at 170 ° C. for 2 hours in a nitrogen atmosphere, and then subjected to solid phase polymerization at 220 ° C. for 10 hours to obtain granular polyethylene terephthalate. It was. The intrinsic viscosity of the polyethylene terephthalate was 0.761 dl / g, and the hue b value was 0.0. After the polyethylene terephthalate was dried at 170 ° C. for 5 hours in a dryer, a 5 mm thick haze of a stepped square plate-shaped molded product formed by an injection molding machine (M-70A manufactured by Meiki Seisakusho Co., Ltd.) 4%. Polyethylene terephthalate with sufficient quality for use with beverage PET bottles.
[Comparative Example 1]

The same operation was performed except that the polyethylene terephthalate-treated body was not used as a raw material in Example 7 and the raw material polyethylene terephthalate flakes of Example 1 were used as they were without being treated. Table 1 shows the analysis results of the raw material polyethylene terephthalate flakes. In the terephthalic acid obtained by hydrolysis, the metal remained as follows, and as such, it was impossible to use it as a polyethylene terephthalate polymerization raw material for producing a high-quality PET bottle for beverages. The remaining metals were antimony = 15 ppm, Ge = 0.5 ppm, Co = 1 ppm, and P = 12 ppm.

    According to the method of the present invention, the polyalkylene terephthalate waste is treated with alkylene glycol to selectively remove the metal such as catalyst derived during the production of polyalkylene terephthalate contained in the polyalkylene terephthalate. By performing a depolymerization reaction using the obtained polyalkylene terephthalate-treated product as a raw material, a high-purity raw material monomer can be recovered. Therefore, since the raw material monomer recovered from polyalkylene terephthalate waste can be used as it is for polyalkylene terephthalate polymerization, it produces polyalkylene terephthalate fibers with good color tone, films with good hue and transparency, and hollow molded articles. become able to. As a result, good recycling of polyalkylene terephthalate waste can be achieved, resource saving can be achieved, and environmental conservation can be contributed.

It is a schematic explanatory drawing of an example of the equipment for enforcing the hydrolysis method of the present invention. FIG. 2 is a perspective view of a stepped square plate-like molded product. Part A has a thickness of about 6.5 mm, part B has a thickness of about 5 mm, and part C has a thickness of about 4 mm. The haze of the molded product was measured using this B part.

Explanation of symbols

1: EG treatment tank, 2: solid-liquid separator, 3: EG rectifier, 4: resin feeder, 5: depolymerization reactor, 6: solid-liquid separator, 7: dryer, 8: water feeder 9: Water rectifier, 10: PET supply line, 11: EG extraction line, 12: Terephthalic acid extraction line

Claims (8)

A method for purifying polyalkylene terephthalate, comprising reducing the amount of metal contained by heating and stirring the polyalkylene terephthalate in alkylene glycol at a temperature of 100 ° C. to 180 ° C. . The molecular weight of the polyester having polyalkylene terephthalate as a main component is M _R before heating and stirring, and M _T / M _R <1 holds when M _T after heating and stirring. Polyalkylene terephthalate treatment method.   The polyalkylene terephthalate treatment method according to claim 1, wherein the polyalkylene terephthalate is polyethylene terephthalate, and the alkylene glycol used in the heating and stirring step is ethylene glycol.   The metal compound derived from the esterification and / or polycondensation catalyst is Al, Ba, Ca, Cd, Ce, Co, Ge, K, Li, Mg, Mn, Na, P, Pd, Sb, Sn, Ti, Zn. 4. The polyalkylene terephthalate treatment method according to claim 1, wherein the polyalkylene terephthalate treatment method is any one of the above or a combination thereof. The polyalkylene terephthalate processing body processed by the method in any one of Claims 1-4.   A method for recovering a monomer component, wherein the polyalkylene terephthalate-treated product according to claim 5 is used as a raw material for a process of depolymerizing terephthalic acid and alkylene glycol.   The reproduction | regeneration method of the monomer component which uses the terephthalic acid and / or alkylene glycol obtained using the polyalkylene glycol processing body of Claim 5 as a raw material as a polyalkylene terephthalate manufacturing raw material. The method for recovering a monomer component according to claim 6, wherein the depolymerization process is hydrolysis without using a substantial decomposition catalyst.

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