JP2000169623A - Chemical recycle of polyethylene terephthalate waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-purity polyethylene terephthalate by utilizing a used polyethylene terephthalate as bis-β-hydroxyethyl terephthalate. SOLUTION: This method comprises a pretreatment process for obtaining a crude polyethylene terephthalate, a depolymerization process for producing a crude bis-β-hydroxyethyl terephthalate (BHET) by adding an excess ethylene glycol for depolymerization, a foreign substance-removing process for removing the foreign plastics and solid foreign substances and/or precipitates other than the polyethylene terephthalate resin, a concentrated BHET producing process by distillation and vaporization, a vacuum vaporization process for obtaining a refined BHET, and a melt-polycondensation process for obtaining a high-purity polyethylene terephthalate polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling used polyethylene terephthalate.

[0002]

2. Description of the Related Art The consumption of polyethylene terephthalate products (bottle containers, films, fibers, etc.) is increasing year by year, and especially the consumption of polyethylene terephthalate bottles (pet bottles) is remarkable. 200,000 tons in 1997, 260,000 tons in 1998, and 300,000 tons in 2000. The consumption of polyethylene terephthalate products is expected to increase year by year, and improving the recovery rate and recycling rate of used polyethylene terephthalate products is an essential proposition on a global scale.

[0003] Speaking of PET bottles, one of the polyethylene terephthalate products, recently, the separate collection and recycling of used PET bottles have become mandatory by law.
The government and the private sector are working together to collect and recycle used PET bottles, but at present the recycling rate is about 5-7%, which is lower than in other countries, and is still at target. At present, it has not been reached. To improve the recovery rate, the government and the private sector need to work together to create an effective collection system.On the other hand, increasing the recycling rate of collected PET bottles also saves resources,
This is a major issue from the viewpoint of energy saving.

Conventionally, collected PET bottles are sorted, reduced in volume and compressed by municipalities, and bale of PET bottles (for example,
0x40x60cm) and handed over to re-commercialization companies. The re-commercialization company unpacks this and separates foreign substances such as metal and PVC bottles, and after washing, separates the colored bottles and then pulverizes them to separate labels, aluminum and the like. Further, after washing, plastics other than polyethylene terephthalate are separated, dehydrated and dried, and then metal is further separated by magnetic force to form flakes or pellets.

[0005] The flakes are sent to a user, who uses the flakes or pellets as raw materials to produce products other than PET bottles such as carpets, packaging films for eggs and the like, and short fibers.

[0006]

However, the above-mentioned conventional recovery and material recycling method has the following problems. First, under the current recycling law, garbage,
The collection yield of the re-commercialization company is low due to the large amount of foreign matter, and the problem of foreign matter incorporation has not been completely solved. In addition, since the types of products that can be regenerated from flakes or pellets are limited for sanitary reasons or the like, there is a problem that the sales market is small. For this reason, at present, PET bottles are only slightly recycled. In addition, plastic bottles other than Class 2 designated PET bottles (for soft drinks, soy sauce, and sake) currently subject to separate collection and recycling, such as cooking oil, mayonnaise, and PET bottles that cannot be easily washed for dressing purposes However, this type of PET bottles cannot be processed by current recycling methods.

[0007] As described above, all of the currently produced and marketed PET bottles are generally used after being used unless the PET bottles can be recycled.
It is industrial waste, and some that are currently collected and recycled are destined to become general waste. This is the same for other polyethylene terephthalate products. This kind of general / industrial waste requires final disposal such as incineration or landfill. However, these treatments involve the problem of environmental pollution, and it is difficult to continue as it is. In addition, in such a processing method, resource saving,
A major problem remains from the viewpoint of energy saving.

Accordingly, the present invention provides a method for producing a high-purity polyethylene terephthalate product again using a used PET bottle recovered from the city as bis-β-hydroxyethyl terephthalate, which is an intermediate material for producing a polyethylene terephthalate product. The challenge is to

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, as a result of diligent studies on a method for obtaining a high-purity polyethylene terephthalate intermediate material and a product using a polyethylene terephthalate waste containing impurities and foreign substances as a starting material, The invention employs the following configuration. That is, the method for recycling polyethylene terephthalate according to the present invention comprises a pretreatment step of subjecting used polyethylene terephthalate waste to pretreatment such as grinding, washing, and foreign matter separation to obtain crude polyethylene terephthalate flakes, and the obtained crude polyethylene. A depolymerization step of adding excessively purified and / or crude ethylene glycol to terephthalate flakes and depolymerizing in the presence of a catalyst to obtain crude bis-β-hydroxyethyl terephthalate (BHET);
From the resulting mixed solution of two kinds of crude BHET and crude ethylene glycol, different plastics such as polyethylene, polystyrene, polypropylene, and vinyl chloride other than polyethylene terephthalate resin and / or solid foreign matter such as metal, glass, and sand and / or precipitates A foreign matter removing step of removing substances, a pre-purification step of removing colored substances and / or dissolved ions from the obtained binary mixture solution of crude BHET and crude ethylene glycol, and a binary mixture solution having passed through the pre-purification step. Ethylene glycol is evaporated and distilled off by distillation and evaporation to obtain concentrated BHET, or BHET is crystallized by cooling the mixed solution to 10 ° C or lower, and then solid-liquid separation of ethylene glycol and BHET is performed. A BHET concentration step of obtaining concentrated BHET by BHET purification step of obtaining purified bis-β-hydroxyethyl terephthalate by evaporating in vacuo such that the concentration of BHET in the evaporator is not more than 10 minutes at a temperature of not more than 250 ° C. and not more than 250 ° C. A high-purity polyethylene terephthalate polymer from waste polyethylene terephthalate through a polyethylene terephthalate polymer production step of performing melt polycondensation using purified BHET and / or the concentrated BHET obtained in the BHET concentration step as a raw material to obtain a high-purity polyethylene terephthalate polymer It is characterized by obtaining.

[0010] The crude polyethylene terephthalate flakes obtained in the pretreatment step are melted in a water-rich state to the extent of centrifugal dehydration and simultaneously hydrolyzed to give a polyethylene terephthalate melt having a low degree of polymerization. It is effective to carry out a depolymerization treatment with ethylene glycol.

The crude BH obtained through the foreign matter removing step
The concentration of crude BHET in a mixture of two kinds of ET and crude ethylene glycol is 10 to 50 wt%, preferably 15 to 35 wt%, the adsorption and / or ion exchange function at 100 ° C. or less is exhibited, and the crude BHET is crystallized. The pre-purification process is performed at a temperature not using a known adsorbent and / or ion exchange resin to remove coloring matter and / or dissolved ions.
Ethylene glycol is evaporated and distilled off by performing an evaporation operation to obtain concentrated BHET, or
After cooling to below ℃ to crystallize BHET, concentrated BH
ET was obtained and the concentrated BHET was heated above 190 ° C to 250
At a temperature of not more than 10 ° C. and in a vacuum so that the residence time of the concentrated BHET in the evaporator is not more than 10 minutes.
It is preferably β-hydroxyethyl terephthalate.

The ethylene glycol separated in the BHET concentration step is directly recycled to the depolymerization step again, or the recycled and / or purified ethylene glycol is purified by a known operation such as distillation, and then the depolymerization step is performed again. It is economical to recycle to

[0013] Most of the bottoms generated in the BHET purification step and / or most of the bottoms generated in purifying the ethylene glycol separated in the BHET concentration step may be recycled to the depolymerization step again. It is effective in improving the yield.

In the foreign matter removing step, different plastics other than polyethylene terephthalate, such as polyethylene, polystyrene, polypropylene and vinyl chloride, which are mixed in the polyethylene terephthalate waste, are compatible with each other, easily become a eutectic mixture, and are depolymerized. After the completion of the reaction, it is insoluble in a mixed solution of two kinds of crude BHET and crude ethylene glycol, and has a specific gravity smaller than that of the two kinds of mixed solutions. Therefore, as a eutectic mixed floating layer of a different plastic other than polyethylene terephthalate. Since the layers are separated, if the eutectic mixed suspended matter layer is extracted from the depolymerization tank, the different plastics can be effectively removed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to specific examples. FIG. 1 is a flowchart specifically showing the recycling method of the present invention. In this embodiment, a bale obtained by reducing the volume of a used PET bottle and compressing it is used as a starting material. This PET bottle veil is manufactured by a known method currently used by municipalities. Of course, other polyethylene terephthalate waste may be used as the starting material instead of the PET bottle veil, and flakes of the PET bottle may be used as the starting material.

[0016] The PET bottle bale obtained by reducing the volume of the PET bottle waste is continuously unloaded into a pulverizer without being packed in a bale state, and warm water or room temperature water or hot water or room temperature water containing a detergent is injected. Crush in water. As described above, since the PET bottle bale is crushed without being unpacked, the workability is improved, and the safety and health measures are also effective. Further, the cleaning effect is extremely enhanced by using the energy of mixing and friction at the time of pulverization, and edible oil and machine oil are easily removed by the cleaning agent. Therefore, a high degree of cleaning effect can be obtained.

Further, the mixture of the flakes of the PET bottle discharged from the crusher and the washing water is immediately subjected to a specific gravity separation treatment to separate the flakes from impurities such as metal, stone, glass, sand. Next, the flakes and the washing water are separated, and the flakes are rinsed with ion-exchanged water and centrifugally dehydrated. The separated washing water and the rinse water after use are filtered, reused as the above-mentioned water for underwater grinding, and the wastewater is subjected to wastewater treatment. In this way, the pretreatment step is greatly simplified.
Therefore, automation of this pretreatment step can be easily achieved. In addition, since such effective pulverization and washing are performed, according to the present invention, there is no problem even if the contents of the plastic bottle remain.

The crude polyethylene terephthalate flake obtained in the above pretreatment step is depolymerized.
It is melted in a water-rich state of the degree of centrifugal dehydration and simultaneously hydrolyzed to give a polyethylene terephthalate melt having a low degree of polymerization, and the polyethylene terephthalate melt is converted into a known esterification catalyst, in the presence of a known catalyst concentration, It is effective to carry out depolymerization by reacting with ethylene glycol. Known esterification catalysts include, for example, zinc acetate, zinc borate, fatty acid salts of zinc, magnesium, calcium, cobalt, antimony, and barium described in "Saturated Polyester Resin Handbook" published by Nikkan Kogyo Shimbun, 1985, zinc, Examples thereof include carbonates of magnesium, calcium, cobalt, antimony, barium, methylates of sodium and magnesium, metallic sodium, metallic magnesium, and oxides of zinc, antimony, lead, and germanium. In particular, according to the present invention, a crystallization-treated and whitened portion can be used without any problem in order to increase the strength and dimensional stability of a PET bottle, and the crystallization treatment and the depolymerization of the whitened portion This method is effective for

The melted and hydrolyzed polyethylene terephthalate melt having a low degree of polymerization is depolymerized with an excess of ethylene glycol to obtain a mixed solution of crude BHET and crude ethylene glycol. Different plastics other than polyethylene terephthalate brought in by polyethylene terephthalate waste may be mixed in this two-component mixed solution, but different plastics other than polyethylene terephthalate such as polyethylene, polystyrene, polypropylene, and vinyl chloride are compatible with each other. And is insoluble in the binary mixture of crude BHET and crude ethylene glycol, and easily at the top of the binary mixture as a eutectic mixed suspension of different plastics due to the specific gravity difference between the binary mixture and the binary mixture. Since the layers are separated, if the eutectic mixed suspended matter layer is extracted from the depolymerization tank, the different plastics can be effectively removed.

It is generally said that a considerable amount of linear oligomers having a degree of polymerization of about 2 to 4 remains in crude BHET obtained by depolymerization of polyethylene terephthalate. By appropriately selecting the ratio, the depolymerization temperature and pressure, and the depolymerization catalyst, the linear oligomer can hardly remain in the crude BHET obtained by the depolymerization of the present method. Preferred for.

Usually, in the crude BHET, about several percent of cyclic oligomers are present in addition to linear oligomers. This cyclic oligomer has a melting point much higher than polyethylene terephthalate, 325-327 ° C,
It has an adverse effect on products during and after molding of PET bottles. According to the present invention, purified bis-β-hydroxyethyl terephthalate containing no such cyclic oligomer can be obtained, so that extremely high quality polyethylene terephthalate can be obtained.

After the completion of the depolymerization reaction, the temperature of the mixed solution of the crude BHET and the crude ethylene glycol is lowered, and the mixture is filtered to obtain unreacted linear and cyclic oligomers as high melting point precipitates.
Removal of solid foreign substances other than polyethylene terephthalate, such as solidified solids of residual plastics and metals, followed by adsorption and ion exchange treatment to remove colored substances and dissolved ions, thereby removing harmful foreign substances contained in crude BHET. Can be completely removed.

The pre-purification step removes coloring agents and / or coloring matters due to thermal deterioration of organic substances accompanying the raw materials, and further removes sugars, salts, and the like adhering to polyethylene terephthalate.
It removes both catalyst ions, polymerization stabilizers and other positive and negative ions from other processes during the polymerization of polyethylene terephthalate. The pre-purification step is very important and the crude BH
In the case where only the decolorizing treatment is performed in the mixed solution of two kinds of ET and crude ethylene glycol to evaporate and distill ethylene glycol, the crude BHE is heated at a temperature exceeding 110 to 120 ° C.
The two-component mixed solution of T and crude ethylene glycol is colored light brown to brown. The cause was found to be due to the thermal decomposition coloring behavior involving both the positive and negative ions, and in addition, the formation of scale on the heat transfer surface in the vacuum evaporation process of concentrated BHET and the prevention of decomposition and polymerization of BHET were prevented. However, they have found that the process can be stabilized and the purity of purified BHET can be maintained, and the present invention has been accomplished.

[0024] Since such effective foreign matter removal and pre-refining is performed, the incorporation of different plastics other than polyethylene terephthalate is allowed. The types of objects are expanded to all PET bottles, not just the second type designated containers, and it is possible to greatly improve the recycling rate of PET bottles. Also, regarding the method of reducing the volume of plastic bottle waste currently being implemented by municipalities,
Currently, only the side compression method is adopted due to restrictions from the plastic bottle waste recycling process, but according to the present invention, the lantern compression method, the oblique rotation cutting compression method, the heat cutting compression method, etc. Various volume reduction compression methods become possible, and the transportation freight cost of PET bottle waste at the time of re-commercialization is greatly reduced, so that the economic effect is very large.

The crude BHE obtained through the above pre-purification step
A binary mixture of T and crude ethylene glycol is distilled and evaporated to separate and distill ethylene glycol to obtain concentrated BHET, or the binary mixture is cooled to 10 ° C. or lower to crystallize BHET. BHET is concentrated by subjecting ethylene glycol and BHET to solid-liquid separation.
The concentrated BHET was evaporated under vacuum at a temperature of more than 190 ° C. and 250 ° C. or less and the residence time of the concentrated BHET in the evaporator was 10 minutes or less, and purified bis-β-
Obtain hydroxyethyl terephthalate.

BHET is very unstable thermally, and its vacuum evaporation is performed at 190-250 ° C., 0.1-0.5 m
Rapid evaporation under mHg conditions is required.
During vacuum evaporation, catalysts, stabilizers, and impurities mixed in the raw material polyethylene terephthalate waste during the polymerization of polyethylene terephthalate are concentrated and fixed on the heat transfer surface of the evaporator, causing various troubles. In evaporation under a high vacuum, these impurities are scattered and entrained and mixed into purified BHET, or the production of ethylene glycol by polycondensation of BHET, etc., lowers the capacity of the vacuum system, increases the evaporation temperature,
This leads to thermal decomposition of HET, which not only causes a vicious cycle of hindering further heat transfer to the evaporator, but also causes clogging of the bottom of the evaporator. In the present invention, since the coloring matter and the dissolved ions are removed by performing the adsorption treatment and the ion exchange treatment as described above, the life of the vacuum evaporator can be improved.

In the above-mentioned vacuum evaporation, it is desirable to reduce the temperature and the residence time as much as possible.
Suitably, it is about 5 mmHg. The residence time is preferably as short as possible, but there is a physical limit, and it is appropriate to keep the residence time within 10 minutes depending on the processing capacity of the vacuum evaporator, latent heat of evaporation, and the like.

When purified BHET of high purity is obtained as described above, the purified BHET is charged into a melt polycondensation reactor to obtain a high-purity polyethylene terephthalate polymer.

In the present invention, as described above, a high-purity polyethylene terephthalate polymer is produced from polyethylene terephthalate waste through purified BHET, and the advantages are as follows. That is, since BHET is formed by using polyethylene terephthalate and ethylene glycol, and this BHET is converted into polyethylene terephthalate and ethylene glycol again, by-products do not occur and replenishment of ethylene glycol is basically unnecessary. Also, BHE
When a polymerization catalyst is added to T and heat polymerization is performed under vacuum,
Since there is no cyclic oligomer in HET, a high quality polyethylene terephthalate polymer is obtained.

FIG. 1 shows a process for producing various polyethylene terephthalate products using the high-purity BHET obtained by the above-mentioned recycling process as an intermediate material. The polyethylene polymer (polymer) obtained from the high-purity BHET as an intermediate material is shown in FIG. Various types of polyethylene terephthalate film product groups can be made into polyethylene terephthalate film by film forming equipment, and the above polymers can be used as raw material for polyethylene terephthalate yarn and cotton in yarn making equipment, such as high-grade textile clothing, carpets, tire cords, automobile interior materials, etc. It can also be a product. Further, the above-mentioned polymer can be used as a raw material for a group of engineering plastic products and a group of plastic bottle products by performing necessary treatment in a solid-phase polymerization facility.

According to the recycling method of the present invention, since the used polyethylene terephthalate product can be returned to the intermediate raw material of the polyethylene terephthalate product group, and then the commercially available polyethylene terephthalate product group can be produced again, almost completely “ A "closed recycling system" is made possible, eliminating the need for incineration and landfilling of used polyethylene terephthalate products as general and industrial waste in the future. For this reason, resource and energy savings, which are the final objectives, can be achieved.

[0032]

[Example] PET bottle bale (bale size: 40 cm × 40 cm × 60) collected and collected separately by municipalities
cm to 18Kg veil) of were charged into a cutter knife with a wet grinder, the plus liquid kitchen detergent 500g in water 1,000 liters, by a pump at a flow rate of 2.3 m ³ / Hr of the wet pulverizer Grinding while circulating between the charging port and the water receiver under the bottom screen of the crusher,
Metal, sand, glass, etc. with high specific gravity are precipitated by a specific gravity separator connected to the crusher, and a mixture of water and flakes containing detergent is poured from the upper layer on a screen provided on a water receiver, and flakes are added. Was taken out. The flakes were rinsed with pure water and centrifugally dehydrated to obtain recovered flakes.

30 kg of the recovered flakes melted in an undried state was mixed in a 230 liter autoclave equipped with a stirrer in a mixture of 150 kg of ethylene glycol and 150 g of zinc acetate dihydrate, which had been heated to 180 ° C. in advance. After removing a distillate having a boiling point lower than that of ethylene glycol, such as water and acetic acid, the reflux condenser was operated to react at normal pressure at a temperature of 195 to 200 ° C. for 3.5 hours.

After completion of the reaction, the temperature of the reactor contents at 197 ° C. was lowered to 97 to 98 ° C. while stirring, and the mixture was filtered hot with a 325 mesh stainless steel wire mesh filter to remove suspended matters and precipitates.

The filtrate after hot filtration was further cooled to 50 ° C., and after confirming that the crude BHET was completely dissolved, the activated carbon bed and then the anion / cation exchange mixed bed were heated at 50 to 51 ° C. for 30 minutes. And passed through a pre-purification treatment. The coloring test of the pre-purification treatment liquid was visually performed, and the test of the residual ion amount was performed by conductivity measurement. The results of the coloring test were sufficiently pure white and good. In the conductivity test, the value was 200 μSiemens before ion removal, but decreased to 2 μSiemens after ion removal.

The above prepurified solution was again charged into a 230-liter stirred autoclave and heated to distill excess ethylene glycol at 198 ° C. under atmospheric pressure.
A melt of T was obtained.

The resulting melt of concentrated BHET was naturally cooled to 130 ° C. while being stirred in a nitrogen gas atmosphere, and then taken out of the autoclave to obtain a strip of concentrated BHET.

The strips of concentrated BHET obtained were hardly colored. Repeat this strip
After heating and melting to 30 ° C., the mixture was supplied to a thin-film vacuum evaporator by a metering pump, and was then heated at 237 ° C. and 0.5 mmHg abs.
After evaporating the residence time in the thin film evaporator for 5 minutes, the mixture was cooled and condensed to obtain purified BHET. The analysis results of the obtained purified BHET are as follows, and commercially available reagent grade BHE
It was equivalent to the quality of T.

[0039]

[Table 1]

The optical density is a method for evaluating the quality of BHET, and is a value considered to be proportional to the content of the coloring matter. Specifically, the absorbance of a 10% methanol solution of BHET was measured using a cell having a wavelength of 380 nm and a cell length of 10 m.
It is a value measured in m.

Using this purified BHET as a raw material, a beaker scale melt polymerization was carried out to obtain a polyethylene terephthalate polymer. The quality of the resulting polyethylene terephthalate polymer was as follows and was equivalent to the quality of virgin commercial polyethylene terephthalate pellets.

[0042]

[Table 2]

[0043]

Comparative Example Purified BHET was obtained in the same manner as in Example except that the pre-purification treatment in the section [0035] was omitted. The optical density of the obtained purified BHET was 4.677.
After the evaporation was completed, a thin gray-white scale was uniformly observed on the heat transfer surface of the thin film evaporator.
Washing had to be performed with 15% strength sodium hydroxide.

[0044]

As described above, the method for recycling polyethylene terephthalate waste according to the present invention comprises:
Since the used polyethylene terephthalate is once converted into high-purity purified BHET, and these are used as intermediate materials to produce high-purity polyethylene terephthalate products again, it is possible to recycle used polyethylene terephthalate products in a closed recycling system. It is not necessary to incinerate or landfill as general and industrial waste, and it is possible to achieve the desired resource and energy savings. This recycling system not only recycles used bottles, films, clothing, and car interior materials (shredder dust) made of polyethylene terephthalate into high-purity polyethylene terephthalate, but also uses used polyester materials other than polyethylene terephthalate. For example, polybutylene terephthalate, liquid crystal polyester, and polyethylene naphthalate can be recycled to a high-purity polyester material again.

[Brief description of the drawings]

FIG. 1 is a diagram showing a recycling system and a flowchart of the present invention using a PET bottle as an example.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) // B29K 67:00 105: 26 F term (reference) 4F201 AA24 AA50 BA04 BC01 BC12 BC25 BN15 BN29 BP03 BP09 BP11 BP15 BP26 BP27 BP31 BQ44 4F301 AA25 AB03 CA13 CA23 CA27 CA34 CA52 CA62 CA68 CA72 CA73 4J029 AA03 AB04 AB07 AC01 AD01 AD02 AD10 AE01 BA03 HD04 KA03 KG01 KG02 KJ02

Claims (7)

[Claims] 1. A pretreatment step of subjecting used polyethylene terephthalate waste to pretreatment such as grinding, washing, and foreign matter separation to obtain crude polyethylene terephthalate flakes, and excessive purification and / or purification of the obtained crude polyethylene terephthalate flakes. Alternatively, a depolymerization step of adding crude ethylene glycol to carry out depolymerization in the presence of a catalyst to obtain crude bis-β-hydroxyethyl terephthalate (BHET), and in a two-mixed solution of the obtained crude BHET and crude ethylene glycol Polyethylene other than polyethylene terephthalate resin, polystyrene, polypropylene,
A step of removing foreign substances such as vinyl chloride and / or solid foreign substances such as metal, glass and sand, and / or a foreign substance, and a step of removing the obtained crude BHET and crude ethylene glycol from a mixed solution of two kinds. A pre-purification step for removing coloring matter and / or dissolved ions, and a distilling and evaporating operation of the premixed mixed solution to evaporate and distill ethylene glycol to obtain concentrated BHET, or A BHET concentration step of cooling the mixed solution to 10 ° C. or less to crystallize BHET and then separating ethylene glycol and BHET into solid and liquid to obtain a concentrated BHET, and heating the obtained concentrated BHET over 190 ° C. to 250 ° C. or less At a temperature of and at a retention time of concentrated BHET in the evaporator of 10 minutes or less.
a BHET purification step for obtaining β-hydroxyethyl terephthalate, and the obtained purified BHET and / or the BHE
A high-purity polyethylene terephthalate polymer from polyethylene terephthalate waste through a polyethylene terephthalate polymer production step in which the concentrated BHET obtained in the T concentration step is melt-polycondensed as a raw material to obtain a high-purity polyethylene terephthalate polymer. Chemical recycling method for polyethylene terephthalate waste. 2. The crude polyethylene terephthalate flake obtained in the pretreatment step is melted in a water-rich state to the extent of being centrifugally dehydrated and simultaneously hydrolyzed to give a polyethylene terephthalate melt having a low degree of polymerization. 2. The chemical recycling method of polyethylene terephthalate waste according to claim 1, wherein the polymerization treatment is performed with an excess of ethylene glycol. 3. The crude B obtained through the foreign matter removing step.
The concentration of crude BHET in a mixture of two kinds of HET and crude ethylene glycol is 10 to 50 wt%, preferably 15 to 50 wt%.
To 35% by weight, and at a temperature at which the adsorption and / or ion exchange function of 100 ° C. or less is exhibited and the crude BHET does not crystallize, a known adsorbent and / or an ion exchange resin is used to remove the coloring matter and / or dissolved ions. The chemical recycling method for polyethylene terephthalate waste according to claim 1 or 2, wherein the polyethylene terephthalate waste is removed. 4. The ethylene glycol separated in the BHET concentration step is directly recycled to the depolymerization step again, or the ethylene glycol is purified by a known operation such as distillation and then recycled to the depolymerization step again. A chemical recycling method for the polyethylene terephthalate waste according to claim 1. 5. Most of the bottoms generated in the BHET purification step and / or most of the bottoms generated in purifying ethylene glycol separated in the BHET concentration step are recycled to the depolymerization step again. A method for chemically recycling polyethylene terephthalate waste according to any one of claims 1 to 4. 6. In the foreign matter removing step, different plastics other than polyethylene terephthalate mixed in polyethylene terephthalate waste are insoluble in a mixed solution of two kinds of crude BHET and crude ethylene glycol after completion of the depolymerization reaction. And, after layer separation as a eutectic mixed floating layer of a different plastic other than polyethylene terephthalate having a lower specific gravity than the two-mixed solution, the eutectic mixed floating layer is extracted from the depolymerization tank and removed. 1
6. The chemical recycling method for polyethylene terephthalate waste according to any one of claims 1 to 5. 7. A packing bale of polyethylene terephthalate waste is put into a crusher in an unpacked state without being unpacked, and the polyethylene terephthalate waste is crushed while containing hot water, room temperature water, or a detergent in the crusher. After injecting warm water or room temperature water, and mixing and friction at the time of pulverization to wash and remove adhered foreign substances on the inner and outer surfaces of polyethylene terephthalate and / or the content residue in the polyethylene terephthalate container, plastics and metals, glass,
The chemical recycling method for polyethylene terephthalate waste according to any one of claims 1 to 6, wherein sand and the like are separated by specific gravity, plastics are rinsed with clear water, and dehydrated to obtain flakes of polyethylene terephthalate waste.