JP2015172113A - Method for producing hydrolyzate of polyester resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a hydrolysate, by which a material to be processed including a polyester resin can be processed by use of chemical recycling techniques without requiring a large-scale apparatus or a cost, and a constituent raw material of the polyester resin can be recovered with high quality.SOLUTION: The production method of a hydrolysate of a polyester resin includes at least: a first step of exposing a material to be processed including a polyester resin such as polyethylene terephthalate to a steam environment to hydrolyze to obtain a first hydrolysate; and a second step of further hydrolyzing the first hydrolysate to obtain a second hydrolysate.

Description

  The present invention relates to a method for producing a hydrolyzate of a polyester-based resin, for example, a treatment method for obtaining a raw material terephthalic acid from a polyethylene terephthalate molded article such as a beverage bottle, film, or sheet.

Polyester resins are widely used for various applications because of their excellent properties. For example, polyethylene terephthalate (PET) is produced and used in large quantities in the food field as life-related materials such as fibers, films, and resins, especially as bottles for drinking water and carbonated drinks because of its excellent chemical stability. Has been. However, disposal of fibers, films, resin product waste, non-standard molded products, etc., which are generated in large quantities with increasing production and usage, is now becoming a major social problem, and resources are effective. From the viewpoint of utilization, a method for effectively recycling these polyester-based resin molded products is required.
As such a recycling method, various methods such as material recycling and chemical recycling have been proposed.

  Material recycling involves melting and reusing at a high temperature without decomposing the polyester-based resin, so that there is a problem that the quality deteriorates due to the heat history. In addition, when a component (impurity) other than the polyester-based resin is contained, it is difficult to completely remove the impurity, and there is a problem that the quality further deteriorates. Therefore, it is difficult to obtain the same quality as the polyester-based resin before recycling except in some cases (such as using the runner generated during injection molding as it is after pulverization).

  On the other hand, chemical recycling can generally be classified into four types: (1) conversion to raw materials, (2) conversion to reducing agents, (3) gas / oil conversion, and (4) thermal recycling. Among these, the use of raw materials is advantageous because a material having the same quality as that of the polyester resin before recycling can be obtained.

  In Patent Document 1, as an example of making polyethylene terephthalate as a raw material, polyethylene terephthalate is decomposed to dimethyl terephthalate and further to terephthalic acid by ethylene glycol (EG) decomposition / methanol treatment, and again polycondensed with EG. A method of “bottle to bottle” is disclosed.

  Patent Document 2 reports that when terephthalic acid is added to polyethylene terephthalate resin and hydrolyzed in hot water at 300 ° C., terephthalic acid can be obtained in a yield of 100% in 10 minutes.

  And in patent document 3, the to-be-processed object containing polyethylene terephthalate resin is exposed in the water vapor | steam atmosphere satisfy | filled with the pressure of the saturated water vapor pressure in process temperature, The said to-be-processed object is by the saturated water vapor | steam generate | occur | produced at the process temperature. A method is disclosed in which a polyethylene terephthalate resin contained therein is hydrolyzed to separate and collect ethylene glycol as a gas or liquid component and terephthalic acid as a solid component.

JP 2003-119316 A JP 2007-332361 A JP 2008-308416 A

However, the method of Patent Document 1 has problems such as complicated operations and high costs, and a large amount of capital investment. The method of Patent Document 2 is a high temperature of 150 to 350 ° C. in a non-dicarboxylic acid-added system. It has been shown that when polyester is hydrolyzed in water, it cannot be sufficiently hydrolyzed, suggesting that dicarboxylic acid as a hydrolysis catalyst is indispensable for hydrolysis in high-temperature water.
In addition, the method of Patent Document 3 has to prepare a pressure-resistant processing chamber provided with a stirring means inside and a cooling tower for recovering ethylene glycol, and the apparatus is large and there is room for improvement. Moreover, when a polyethylene terephthalate resin contains an impurity, there exists a problem that the quality of the collect | recovered terephthalic acid and ethylene glycol falls.

  Polyester resins use limited petroleum resources, and the establishment of chemical recycling technology for polyester resin waste is an urgent issue in order to build a society that can sustain its supply. However, as described above, the establishment of a method in which both maintenance of quality and economy (suppression of running cost and initial cost) have not been established yet, and its development is urgently required.

  Therefore, an object of the present invention is to treat an object to be treated containing a polyester resin by chemical recycling technology without using a large-scale apparatus and cost, and without using a special hydrolysis catalyst. An object of the present invention is to provide a method for producing a hydrolyzate of a polyester-based resin capable of recovering constituent materials with high quality.

  As a result of intensive studies in view of the above problems, the present inventors first exposed a hydrolyzed polyester resin molded article (object to be treated) to a water vapor atmosphere to obtain a first hydrolyzate, and this It has been found that the above-mentioned problem can be solved by having a two-step process of hydrolyzing the first hydrolyzate in hot water, and has completed the present invention.

That is, the present invention is achieved by the following (1) to (9).
(1) A first process for obtaining a first hydrolyzate by exposing a treatment object containing a polyester-based resin to a steam atmosphere to hydrolyze, and heating the first hydrolyzate in hot water. A method for producing a hydrolyzate of a polyester resin, comprising at least a second step of further hydrolyzing the first hydrolyzate to obtain a second hydrolyzate.
(2) The production according to (1), wherein the polyester-based resin is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polytrimethylene terephthalate. Method.
(3) The production method according to (2), wherein the polyester-based resin is polyethylene terephthalate.
(4) The production method according to (3), wherein the first hydrolyzate includes an oligomer produced by decomposition of the polyethylene terephthalate.
(5) The production method according to (3), wherein the second hydrolyzate contains terephthalic acid and ethylene glycol.
(6) The manufacturing method according to any one of (1) to (5), wherein the first step is performed at a steam atmosphere temperature of 100 to 260 ° C.
(7) The manufacturing method according to any one of (1) to (6), wherein the second step is performed at a hot water temperature of 150 to 300 ° C.
(8) The manufacturing method according to any one of (1) to (7), wherein the first step and the second step are continuously performed in a pressure-resistant container.
(9) In the pressure-resistant container, a first container having a hole through which the object to be processed and a first hydrolyzate can be passed, and a lower part of the first container, the first container A second container for receiving the first hydrolyzate that has passed through one container is installed, the object to be treated is accommodated in the first container, the first step is performed, and then the second container is present in the second container. The production method according to (8), wherein the second step of further hydrolyzing the first hydrolyzate in hot water to obtain a second hydrolyzate is performed.

  The method for producing a hydrolyzate of a polyester resin according to the present invention includes a first step in which an object to be treated is hydrolyzed by exposure to a steam atmosphere to obtain a first hydrolyzate, and the first hydrolysis The product is heated in hot water, and the first hydrolyzate is further hydrolyzed to have a second step of obtaining a second hydrolyzate. In the first step, the polyester resin in the object to be treated is decomposed by water vapor and oligomerized. The oligomer is further hydrolyzed in hot water in the second step, whereby among the constituent materials of the polyester resin, water-soluble ones are dissolved in hot water, and water-insoluble ones are hot water. Thus, each raw material can be recovered with high quality without any cost.

  This is also the case when a polyester resin, which is used in a large amount and is difficult to process due to its amount, such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate or polytrimethylene terephthalate is used as the object to be treated. However, the constituent materials can be recovered with high quality without cost.

  When the polyester resin is polyethylene terephthalate (PET), first, the ester bond of PET is broken by hydrolysis in the first step, and an oligomer containing an ethylene glycol unit and an oligomer containing a terephthalic acid unit are generated. In the second step, these oligomers are hydrolyzed into hot ethylene water to ethylene glycol monomer units and terephthalic acid monomer units. The ethylene glycol monomer units are dissolved in hot water and the terephthalic acid monomer units are solidified in hot water. , Each can be recovered with high yield.

  Moreover, if the said 1st process and a 2nd process are continuously performed within a pressure-resistant container, the stirring means of the patent document 3, a cooling tower, etc. will not be required, but it is low-cost, high quality, and high It becomes possible to process with a recovery rate.

It is a flowchart for demonstrating the manufacturing method of the hydrolyzate of the polyester-type resin of this invention. It is a figure for demonstrating the manufacturing method in the suitable form of this invention. In an Example, it is a graph which shows the heat history of the water vapor | steam atmosphere temperature in the pressure-resistant container after starting a test object in a pressure-resistant container, and a test start, and the change of a gauge pressure. In the examples, the composition of the hydrolyzate (solid) in the second container at the time when 1 hour, 2 hours, 3 hours, and 5 hours passed after the water vapor atmosphere temperature reached a constant temperature (about 206 ° C.) was determined by HPLC. It is a graph which shows the result investigated by (1). In Example 1 and Comparative Example 1, the result of examining the composition of the hydrolyzate (solid) in the second container when 3 hours had elapsed after the water vapor atmosphere temperature reached a constant temperature (about 206 ° C.). It is a graph which shows.

Hereinafter, the to-be-processed object used for the manufacturing method of the hydrolyzate of the polyester-type resin of this invention is demonstrated in detail.
The object to be treated (polyester-based resin molded product) containing the polyester-based resin used in the present invention is not particularly limited with respect to the type and raw materials other than the polyester-based resin contained therein, and is conventionally known or publicly used. It can be various processed objects.

  For example, as the polyester resin, for example, a thermoplastic resin having an ester bond site by a reaction (polycondensation) between a polyol component and a polycarboxylic acid component can be mentioned. Examples of the polyol component include ethylene glycol, 1, 3-trimethylene glycol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 2,2-dimethyl-1,3-propanediol, 1, 6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,7-heptanediol, 2,2-diethyl-1,3-propanediol, 2-methyl 2-propyl-1,3-propanediol, 2-methyl-1,6-hexanediol, 1,8-oct Diol, 2-butyl-2-ethyl-1,3-propanediol, 1,3,5-trimethyl-1,3-pentanediol, 1,9-nonanediol, 2,4-diethyl-1,5-pentane Aliphatic diols such as diol, 2-methyl-1,8-octanediol, 1,10-decanediol, 2-methyl-1,9-nonanediol, 1,18-octadecanediol, dimer diol; Cycloaliphatic diols such as cyclohexanediol, 1,3-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol; bisphenol A, Ethylene oxide adduct of bisphenol A, bisphenol S, bisphenol S Ethylene oxide adducts, xylylene diol, an aromatic diol such as naphthalene diol; diethylene glycol, triethylene glycol, polyethylene glycol, a diol component such as ether glycol and dipropylene glycol. In addition, as a polyol component, the polyol component of polymer forms, such as polyether polyol and polyester polyol, may be sufficient. Examples of the polyether polyol include polyether diols such as polyethylene glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran and the like, polypropylene glycol, polytetramethylene glycol, and copolyether obtained by copolymerization thereof. Can be mentioned. Furthermore, examples of the polyol component include glycerin, trimethylolpropane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, and the like. A trihydric or higher polyhydric alcohol may be used.

  Examples of the polycarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid. Aliphatic dicarboxylic acids such as oxalic acid, succinic acid, methyl succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid; Examples include dicarboxylic acid components such as alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid. Furthermore, as the polycarboxylic acid component, for example, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, trimellitic acid, pyromellitic acid, etc. A trivalent or higher polyvalent carboxylic acid may be used. The polycarboxylic acid component may be acid anhydrides or lower alkyl esters of these carboxylic acids.

  The polyol component and the polycarboxylic acid component may be used alone or in combination of two or more.

In addition, biodegradable plastics such as polylactic acid, polybutylene succinate (PBS), polycaloplactone (PCL), polyhydroxyalkanoate (PHA), poly-3-hydroxybutyric acid (PHB) can also be used as the polyester resin. .
The polyester resin may be crosslinked with various crosslinking agents.

  Examples of the polyester resin suitably used from the viewpoint of the effects of the present invention include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polytrimethylene terephthalate, and the like. preferable.

  In addition, the material to be treated containing the polyester-based resin in the present invention is not particularly limited, and various molded products, typically various molded products that have been used and should be reprocessed can be used. Examples thereof include fibers, films, sheets, bottles for drinking water and carbonated drinks, adhesive tapes, food trays, and the like.

In addition, the above various molded products are often blended with raw materials other than polyester resins, such as various additives, depending on the form of use, but the present invention is not limited to the types of raw materials other than these polyester resins. .
Examples of raw materials other than polyester resins include known flame retardants, plasticizers, lubricants, colorants (pigments, dyes, etc.), ultraviolet absorbers, antioxidants, anti-aging agents, fillers, reinforcing agents, and antistatic agents. , Surfactants, tension modifiers, shrinkage inhibitors, fluidity modifiers, surface treatment agents, and the like.

The various molded products can be laminates. That is, a laminate including a polyester resin layer and a layer other than the polyester resin may be used. Specifically, for example, when the object to be treated is an adhesive tape, a laminate of a polyester resin layer and a layer made of, for example, an acrylic adhesive, or a laminate provided with a release layer such as silicone In the present invention, even such a laminate can be treated.
However, from the viewpoint of the effect of the present invention, the ratio of the polyester resin in the object to be treated is, for example, 40% by mass or more, preferably 60% by mass or more.

  In the present invention, the object to be treated may be in the form as it is, but it has an appropriate size so that it can be efficiently decomposed into a hydrolyzate by the first step and the second step of the present invention described below. It is preferable to perform crushing or cutting and washing.

  The method for producing a hydrolyzate of a polyester resin according to the present invention includes a first step of obtaining a first hydrolyzate by subjecting an object to be treated containing a polyester resin to hydrolysis by exposing it to a water vapor atmosphere; And a second step of heating the first hydrolyzate in hot water to further hydrolyze the first hydrolyzate to obtain a second hydrolyzate.

Hereafter, the manufacturing method of the hydrolyzate of the polyester-type resin of this invention is demonstrated in detail.
FIG. 1 is a flowchart for explaining a method for producing a hydrolyzate of a polyester resin of the present invention.
First, the object to be treated is prepared, and the object to be treated is crushed or cut into an appropriate size as needed so that it can be efficiently decomposed into a hydrolyzate by the first step and the second step, and attached to the surface. Impurities and the like are removed by washing (steps S10 and S11). Subsequently, a two-stage hydrolysis reaction is performed on the workpiece by the first step and the second step (steps S12 and S13).

(First step)
In the first step, an object to be treated containing a polyester resin is hydrolyzed by exposure to a steam atmosphere to obtain a first hydrolyzate.
As is well known, hydrolysis is a reaction in which when one bond is cleaved, the bond is ionically cleaved, and the H ₂ O1 molecule is divided into H ⁺ and OH ⁻ and added to the cleavage position. is there.
In the present invention, in the first step, first, the target first hydrolyzate and other impurities are separated by exposing the object to be treated to a water vapor atmosphere. As a 1st hydrolyzate, the hydrolyzate containing the oligomer which a polyester-type resin decomposes | disassembles and contains is made into a fluid state. As a 1st hydrolyzate, the hydrolyzate containing the oligomer which a polyester-type resin decomposes | disassembles and produces | generates is included, and it is made into a fluid state on hydrolysis conditions.

  In the first step of the present invention, the temperature (hereinafter, also referred to as “water vapor atmosphere temperature”) when the workpiece containing the polyester resin is exposed to the water vapor atmosphere is appropriately determined depending on the type of the polyester resin. For example, the temperature is preferably 100 to 260 ° C, more preferably 120 to 260 ° C, and still more preferably 140 to 260 ° C. By carrying out in the temperature range, the polyester resin can be effectively hydrolyzed under a steam atmosphere. In particular, when the polyester-based resin contains polyethylene terephthalate, from the viewpoint of shortening the reaction time and melting point (melting point of polyethylene terephthalate: about 260 ° C.), the water vapor atmosphere temperature is preferably in the range of 150 to 260 ° C., for example. More preferably, it is 180-260 degreeC, More preferably, it is 200-260 degreeC.

  The hydrolysis time is preferably, for example, 1 minute to 20 hours, more preferably 5 minutes to 10 hours. By performing in the said range, the molecular weight of the 1st hydrolyzate obtained can be reduced and the production | generation of a by-product can be suppressed. In particular, when the polyester-based resin contains polyethylene terephthalate, the hydrolysis time is preferably in the range of, for example, 5 minutes to 20 hours, more preferably 10 from the viewpoint of reducing the molecular weight and suppressing by-products. Min to 10 hours.

  In the first step of the present invention, the hydrolysis is preferably performed under saturated water vapor pressure at the water vapor atmosphere temperature under pressure. For example, the saturated water vapor pressure is preferably 0.4 to 5 MPa, and more preferably 1 to 5 MPa. By performing hydrolysis within the above range, the first hydrolyzate can be obtained in a short time.

The water vapor pressure is preferably increased along the saturated water vapor pressure curve, and such a step can prevent the polyester resin as the object to be treated from being carbonized or denatured. Various known means can be employed for the supply of water vapor.
Moreover, in the 1st process in this invention, it is preferable to start a hydrolysis in the state which the to-be-processed object containing a polyester-type resin does not contact with water.
For example, when the polyester-based resin is polyethylene terephthalate, the first hydrolyzate obtained in the first step includes an oligomer produced by the decomposition of polyethylene terephthalate (hereinafter, also simply referred to as “polyethylene terephthalate oligomer”). Including other intermediate products. The oligomer of polyethylene terephthalate is composed of, for example, 2 to 10 monomers (constituent units), and the weight average molecular weight of the oligomer is, for example, 200 to 1000.

  In the present invention, the viscosity of the first hydrolyzate obtained in the first step can be appropriately set depending on the type of the object to be treated and the degree of hydrolysis. Adjust the viscosity to such an extent that the first hydrolyzate can be passed through the hole of the first container on which the object is placed, and the first hydrolyzate and other impurities can be separated. Is preferred.

An object to be processed including a polyester resin is placed in a pressure-resistant container and placed in a first container having a hole that does not allow the object to be processed to pass through and allows the first hydrolyzate to pass through. The hydrolysis is preferably performed in the first container.
The material of the first container is not particularly limited as long as it does not affect the reaction for obtaining the first hydrolyzate, but a container made of metal, ceramics or the like is used.
The shape and size of the hole of the first container are not particularly limited as long as the object to be processed and the first hydrolyzate can be passed therethrough. Examples of the shape include a circle, a polygon, and an indeterminate shape, and the size (maximum length of pores) is preferably set as appropriate according to the viscosity of the first hydrolyzate.

(Second step)
In the subsequent second step of the present invention, the first hydrolyzate is heated in hot water to further hydrolyze the first hydrolyzate to obtain a second hydrolyzate.
By further hydrolyzing the first hydrolyzate in the second step, the hydrolysis efficiency for obtaining the desired hydrolyzate can be increased, and water-soluble impurities mixed in the hydrolyzate can be extracted. And the second hydrolyzate can be obtained with high purity. The second hydrolyzate is preferably a hydrolyzate containing a polyol component and a polycarboxylic acid component, which are constituent materials of the polyester resin. From the hydrolyzate containing the polyol component and the polycarboxylic acid component of the polyester-based resin, the polyol component and the polycarboxylic acid component can be recovered by a fractionation and purification process.

  The second step is preferably performed under pressure. In addition, in the form in which the first step and the second step described below are continuously performed in the pressure-resistant container, the second step can be performed, for example, under the saturated water vapor pressure employed in the first step. As a pressurizing condition, for example, 0.4 to 10 MPa is preferable, and 1 to 10 MPa is more preferable.

The temperature of the hot water is, for example, preferably 150 to 300 ° C, more preferably 180 to 300 ° C, and further preferably 200 to 300 ° C. By carrying out in the temperature range, the molecular weight of the second hydrolyzate can be reduced, by-products can be suppressed, and impurities can be reduced. The heating time in hot water is, for example, preferably 1 minute to 20 hours, more preferably 5 minutes to 10 hours. By performing in the said range, the molecular weight of the 2nd hydrolyzate obtained can be reduced, a by-product can be suppressed, and an impurity can be reduced further.
For example, when the polyester resin is polyethylene terephthalate, the second hydrolyzate obtained in the second step is mostly ethylene glycol and terephthalic acid, which are constituent materials, and is otherwise hydrolyzed in the second step. It contains a small amount of polyethylene terephthalate oligomers and other intermediate products. The water-soluble ethylene glycol is dissolved in hot water, and the water-insoluble terephthalic acid is solid in the hot water and can be collected separately.

The 1st hydrolyzate which passed the 1st container is accommodated in the 2nd container installed in the pressure-resistant container, and also hydrolyzes in hot water. The first hydrolyzate may be accommodated in a second container in which hot water has been put in advance, or hot water may be added to the first hydrolyzate in the second container. In either case, water may be used first instead of hot water, and then heated to become hot water having a temperature within the preferred range of the present invention. Furthermore, dew condensation water generated from water vapor can be used as a substitute for hot water.
The material of the second container is not particularly limited as long as it does not affect the reaction for obtaining the second hydrolyzate, but a container made of metal, ceramics or the like is used.

  Similarly, when the polyester resin is polyethylene naphthalate, the second hydrolyzate containing ethylene glycol and 2,6-naphthalenedicarboxylic acid is used. When the polyester resin is polybutylene terephthalate, 1,4-butanediol and terephthalic acid are used. In the case of polybutylene naphthalate, the second hydrolyzate containing 1,4-butanediol and 2,6-naphthalenedicarboxylic acid is used in the case of polytrimethylene terephthalate. A second hydrolyzate containing 1,3-propanediol and terephthalic acid can be obtained, and the polyol component and the polycarboxylic acid component can be separately recovered.

  In addition, you may collect | recover, after further refine | purifying a 2nd hydrolyzate by a well-known refinement | purification method as needed, and also raising purity.

  When the second hydrolyzate after the second step includes a water-soluble hydrolyzate (for example, ethylene glycol) and a water-insoluble hydrolyzate (for example, terephthalic acid), as described above, The hydrolyzate is dissolved in hot water, and the water-insoluble hydrolyzate is not dissolved in hot water and becomes a solid (steps S14 and S17). The dissolved water-soluble hydrolyzate is subjected to a known purification treatment as necessary (step S15) and recovered (step S16). On the other hand, the solid water-insoluble hydrolyzate is similarly subjected to a known purification treatment as necessary (step S18) and recovered (step S19).

  The first step and the second step may be performed continuously as described below, or the first hydrolyzate obtained in the first step is once recovered and then this first step is recovered. You may employ | adopt what is called a batch type which applies 1 hydrolyzate to a 2nd process.

Next, a further preferred embodiment of the method of the present invention will be described.
According to a preferred embodiment of the present invention, the first step and the second step are continuously performed in a pressure resistant container. The pressure resistant container is preferably provided with a heater. By using a pressure resistant container equipped with a heater, the processing pressure and temperature in the first step and the second step can be arbitrarily adjusted. For example, as described above, an operation for increasing the water vapor along the saturated water vapor pressure curve can be easily performed. Note that the rise and fall of the pressure and temperature can be controlled by appropriately applying known control means. By performing the first step and the second step in one container, a simple processing operation can be performed, and the equipment cost and the processing cost can be reduced.

  In addition, a first container provided with a hole that allows the first hydrolyzate to pass therethrough without passing an object to be processed in the pressure-resistant container, and a second container installed below the first container. The first process is performed on the workpiece in the first container, the first hydrolyzate that has passed through the first container is received by the second container, and the second hydrolyzate in the second container is subjected to the second process. A form in which two steps are performed is more preferable. According to this form, it becomes possible to process the processing object containing the polyester resin more simply, at low cost, with high quality and with a high recovery rate.

FIG. 2 is a diagram for explaining the processing method according to the preferred embodiment of the present invention.
As shown to Fig.2 (a), the 1st container 21 and the 2nd container 22 are installed in the pressure-resistant container 20 provided with the heater (not shown). An object to be processed S is accommodated in the first container 21. Further, hot water W1 is stored in the second container 22. Water W2 for generating water vapor is stored at the bottom of the pressure-resistant container 20. Note that the steam may be supplied into the pressure-resistant container 20 by a steam generator provided outside (not shown). The first container 21 includes a hole A that does not allow the workpiece S to pass therethrough and allows the first hydrolyzate to pass therethrough.

  Subsequently, as shown in FIG. 2B, when the first step is performed, the object to be processed S is hydrolyzed to become the first hydrolyzate H1, and the first container 21 of the first container 21 as shown by the arrow. Drop from hole A. The dropped first hydrolyzate H1 is received in the hot water W1 in the second container 22 and is applied to the second step, whereby a second hydrolyzate is generated in the hot water W1.

Next, as shown in FIG. 2 (c), when the second hydrolyzate includes a water-soluble hydrolyzate and a water-insoluble hydrolyzate, the water-soluble second hydrolyzate H2 is The water-insoluble second hydrolyzate H3 is not dissolved in the hot water W1 and becomes a solid. These second hydrolysates H2 and H3 are recovered by performing a known purification treatment as necessary. When the workpiece S includes polyethylene terephthalate, the water-soluble hydrolyzate contains ethylene glycol, and the water-insoluble hydrolyzate contains terephthalic acid. In the first container 21, the high molecular weight residue S1 that has not been hydrolyzed in the first step remains without passing through the hole A. In addition, after the second step, it is preferable to lower the temperature of the pressure resistant container 20 while controlling the pressure and temperature in the pressure resistant container 20. Deterioration of the quality of the raw material recovered by this operation can be suppressed.
The various conditions for hydrolysis are the same as described above.

  The first container 21 and the second container 22 are preferably made of metal that can sufficiently withstand the hydrolysis conditions of the first process and the second process. For example, the first container 21 is a known punching metal or metal mesh. Etc. can be used.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Example 1
Using an apparatus as shown in FIG. 2, a polyethylene terephthalate adhesive tape was processed as an object to be processed. The pressure-sensitive adhesive tape is a pressure-sensitive adhesive tape using a polyethylene terephthalate film having a thickness of 35 μm and a weight average molecular weight of 20000. An acrylic pressure-sensitive adhesive is applied to one surface of the polyethylene terephthalate film at a rate of 25 g / m ^2. The agent is applied.

First, as shown to Fig.2 (a), the pressure resistant container 20 provided with the heater (not shown), the 1st container 21, and the 2nd container 22 was prepared.
The internal volume of the first container 21 was 10 liters, and 100 g of the adhesive tape was put into it. 100 ml of water was placed in the second container 22. Water W2 for generating water vapor is stored at the bottom of the pressure resistant container 20, and water vapor can be generated by a heater.
The 1st container 21 is provided with the hole A which can let the 1st hydrolyzate produced in a 1st process pass, without letting a processed material pass. The hole A was made of a punching metal made of stainless steel, and the size of the hole A was set to 1 mm square.

Subsequently, as shown in FIGS. 2B and 2C, the first step and the second step were continuously performed in the pressure-resistant container 20. In the first step and the second step, the pressure-sensitive container 20 was hydrolyzed with a polyethylene terephthalate pressure-sensitive adhesive tape under the conditions of a steam atmosphere temperature of 206 ° C., a hot water W1 temperature of 206 ° C., and a saturated steam pressure. At each stage after 1 hour, 2 hours, 3 hours and 5 hours have passed since the water vapor atmosphere temperature in the pressure-resistant container reached 206 ° C, the state of the adhesive tape was observed, and the adhesive tape was taken out and subjected to HPLC. The composition of the hydrolyzate was examined. The HPLC analysis conditions are as follows.
〔Analysis conditions〕
Analytical device: Ultimate Fisher 3000 manufactured by Thermo Fisher Scientific
Column: CAPCELLPAK (registered trademark) (4.6 mmφ × 150 mm, 5 μm, manufactured by Shiseido Co., Ltd.)
Eluent composition: Formic acid aqueous solution / methanol gradient condition Flow rate: 1 mL / min
Detector: DAD (diode array detector, 190 nm to 800 nm, 242 nm extraction)
Column temperature: 40 ° C
Injection volume: 5 μL

  FIG. 3 shows the water vapor atmosphere temperature and gauge in the pressure resistant container 20 at the time when 1 to 5 hours have elapsed since the start of the experiment by putting the workpiece into the pressure resistant container in order to perform the hydrolysis reaction. It is a graph which shows a pressure. 1 hour after the water vapor atmosphere temperature reaches a constant temperature (about 206 ° C.), the first hydrolyzate H1 of the polyethylene terephthalate adhesive tape is the first container 21 as shown by the arrow in FIG. All dropped from the hole A into the second container 22. The dropped first hydrolyzate H1 contained an oligomer of polyethylene terephthalate, and when the oligomer was measured by the GPC method (PMMA conversion), it had a weight average molecular weight of 650. In this way, the first hydrolyzate H1 is received in the hot water W1 of the second container 22, and as shown in FIG. 2 (c), the second step is performed under the same temperature and pressure conditions as described above. It was given to.

FIG. 4 shows the composition of the hydrolyzate (solid) in the second container when 1 hour, 2 hours, 3 hours, and 5 hours have passed since the water vapor atmosphere temperature reached a constant temperature (about 206 ° C.). It is a graph which shows the result investigated by this.
In FIG. 4, TPA indicates terephthalic acid. Similarly, T represents a terephthalic acid unit, E represents an ethylene glycol unit, D represents a diethylene glycol unit, and the oligomer is considered to be formed by combining these units.

From the results shown in FIG. 4, as time elapses after the hydrolysis reaction is performed, more TPA is produced, and 72% by mass can be recovered 3 hours after the water vapor atmosphere temperature reaches a constant temperature (about 206 ° C.). Later, 94% by mass was recovered.
Further, the amount of Si contained in the hydrolyzate (solid) (derived from the back treatment agent applied to the back of the polyethylene terephthalate film) was examined by fluorescent X-ray analysis. As a result, 2 hours after the hydrolysis reaction, the Si amount was 410 ppm, after 3 hours it was 30 ppm, after 5 hours it was 10 ppm, and as the time passed after the hydrolysis reaction was carried out, the amount of impurities (Si) increased. It is found that by further hydrolyzing the first hydrolyzate in hot water W1, impurities such as Si move to the aqueous phase and the purity of TPA as the second hydrolyzate is improved. It was.
Moreover, it was confirmed after the 2nd process completion | finish that the acrylic adhesive which was not hydrolyzed remains in the 1st container 21, without passing the hole A. FIG.

  In the above description, the recovery of TPA is mainly described. However, ethylene glycol, which is a water-soluble second hydrolyzate, cools the hot water W1 in the second container 22 after the second step, and performs distillation or the like. It can collect | recover by performing a well-known purification method.

(Comparative Example 1)
In Example 1, Example 1 was repeated except that the first step was not carried out and a polyethylene terephthalate pressure-sensitive adhesive tape as an object to be treated was put into the hot water W1 of the second container. After the hydrolysis reaction was performed, the hydrolyzate (solid) in the second container was recovered at the time when 3 hours had elapsed after the steam atmosphere temperature reached a constant temperature (about 206 ° C.), and the composition was examined by HPLC. The results are shown in FIG.

  From the results shown in FIG. 5, the amount of TPA produced was significantly reduced compared to Example 1 in Comparative Example 1 in which only the second step was performed without performing the first step. The amount of impurities (Si) was 30 ppm.

  From the above results, it was found that terephthalic acid can be recovered with high quality from a molded article made of polyethylene terephthalate by the two-stage process of the first and second processes in the present invention.

  The present invention provides a processing method for an object to be processed, in which an object to be processed including a polyester resin can be processed without taking a large-scale apparatus or cost, and the constituent materials of the polyester resin can be recovered with high quality. Therefore, chemical recycling technology can help build a society that can sustain a limited supply of petroleum resources.

20 pressure-resistant container 21 first container 22 second container A hole H1 first hydrolyzate H2, H3 second hydrolyzate S object to be treated S1 residue

Claims (9)

A first step of obtaining a first hydrolyzate by subjecting an object to be treated containing a polyester resin to hydrolysis by exposure to a water vapor atmosphere, and heating the first hydrolyzate in hot water, A method for producing a hydrolyzate of a polyester resin, comprising at least a second step of further hydrolyzing 1 hydrolyzate to obtain a second hydrolyzate.   The manufacturing method according to claim 1, wherein the polyester resin is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, and polytrimethylene terephthalate.   The manufacturing method of Claim 2 whose said polyester-type resin is a polyethylene terephthalate.   The production method according to claim 3, wherein the first hydrolyzate includes an oligomer produced by decomposition of the polyethylene terephthalate.   The production method according to claim 3, wherein the second hydrolyzate contains terephthalic acid and ethylene glycol.   The manufacturing method according to any one of claims 1 to 5, wherein the first step is performed at a steam atmosphere temperature of 100 to 260 ° C.   The manufacturing method according to any one of claims 1 to 6, wherein the second step is performed at a hot water temperature of 150 to 300 ° C.   The manufacturing method according to any one of claims 1 to 7, wherein the first step and the second step are continuously performed in a pressure-resistant container. In the pressure-resistant container, a first container provided with a hole that allows the first hydrolyzate to pass through without passing the object to be processed, and the first container at a lower part of the first container. Installing a second container for receiving the first hydrolyzate that has passed through;
Storing the object to be processed in the first container, performing the first step;
The manufacturing method according to claim 8, wherein the second step of obtaining the second hydrolyzate by further hydrolyzing the first hydrolyzate in hot water existing in the second container is performed.

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