JP3831775B2 - Method for purifying bishydroxyalkyl terephthalate - Google Patents

Description

【００２７】
表１に示した結果から明らかなように、活性炭処理単独による比較例１の精製法では、不純物イオンの除去ができないため導電率が高く、イオン交換樹脂単独による比較例２の精製法では、着色剤が吸着されず処理液に色が残る。それに対し、活性炭処理およびイオン交換樹脂処理を行った実施例１、２の処理液は不純物イオンも着色剤も除去されている。
【００２８】
【発明の効果】
粗ＢＨＥＴ等を活性炭とイオン交換樹脂を組み合わせて精製処理することにより、粗ＢＨＥＴ等に含まれる着色剤、不純物イオンを効率的に除去することができる。精製されたＢＨＥＴ等は再生ＰＥＴ等の原料モノマーとして利用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for purifying bishydroxyalkyl terephthalate and an apparatus therefor. More particularly, the present invention relates to a purification method and apparatus of the crude bishydroxyalkyl terephthalate can be used as a raw material for reproduction polyalkylene terephthalate.
[0002]
[Prior art]
Conventionally, polyethylene terephthalate and polybutylene terephthalate (hereinafter abbreviated as “PET”) are reacted with dimethyl terephthalate or terephthalic acid and ethylene glycol or 1,4-butanediol to produce bishydroxyethyl terephthalate or bishydroxybutyl. It is manufactured by producing terephthalate (hereinafter abbreviated as “BHET etc.”) and then condensing BHET etc.
[0003]
Since crude BHET obtained from dimethyl terephthalate or terephthalic acid contains methanol and water as by-products, it was purified by distilling off methanol and water by distillation before condensation.
[0004]
On the other hand, since the Containers and Packaging Recycling Law came into effect in April 1997, the demand for recycling PET and the like has increased. As methods for recycling PET, etc., the recovered PET, etc. is shredded and melted, processed into fibrous PET, etc., and regenerated into a fabric, and the recovered PET, etc. is used as a raw material monomer (BHET, etc.) There is a chemical recycling method that decomposes and recovers, and again synthesizes PET and the like from recovered monomers.
[0005]
As a chemical recycling method for PET or the like, a method for decomposing PET or the like by a solvolysis reaction using a solvent such as alcohol or glycol in the presence of a catalyst and recovering a monomer (BHET or the like) is known. .
[0006]
[Problems to be solved by the invention]
However, monomers recovered by the chemical recycling method (BHET and the like) contain impurities such as various side decomposition products, colorants, deposits, and ions contained in water used during the recycling process. In order to synthesize PET or the like, it is necessary to use a high-purity monomer, and the monomer recovered by the chemical recycling method has many impurities and cannot be used for the synthesis of PET or the like as it is.
[0007]
The problem to be solved by the present invention is to provide a method for purifying crude bishydroxyalkyl terephthalate, which can be a highly pure monomer that can be used in the synthesis of PET and the like.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have intensively studied and as a result, the present invention has been completed.
[0009]
That is, the present invention is applied to a method of purifying crude bishydroxyethyl terephthalate or crude bishydroxybutyl terephthalate obtained by solvolysis of waste polyethylene terephthalate or waste polybutylene terephthalate with activated carbon and an ion exchange resin. A liquid temperature of 70 ° C. or higher is passed, the ion exchange resin is a weakly basic anion exchange resin and a cation exchange resin, and the treatment with activated carbon is performed after treatment with activated carbon, and the bishydroxyalkyl is characterized in that The present invention relates to a method for purifying terephthalate.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The process subject to crude bishydroxyalkyl terephthalate of the present invention, a bis-hydroxyalkyl terephthalate containing impurities, Po Rie Chi alkylene terephthalate or bis-hydroxyethyl terephthalate obtained by hydrolysis or solvolysis, port ribs Chi terephthalate Is bishydroxybutyl terephthalate obtained by hydrolysis or solvolysis.
[0011]
Processed subject to rough BHET or the like of the present invention, in addition to the crude BHET and the like obtained by the chemical recycling process of waste such as PET is also obtainable from dimethyl terephthalate and terephthalic acid of high purity raw material of conventional synthesis such as PET Coarse BHET or the like may be used.
[0012]
The chemical recycling process for PET or the like may be any method that can decompose PET or the like into crude BHET, for example, a solvolysis method such as PET using a solvent, a decomposition method using a supercritical solution, or the like. Can be mentioned.
[0013]
Since the crude BHET decomposed in the chemical recycling step contains PET polymerization catalyst and inorganic pigment as insoluble inorganic impurities, the insoluble inorganic impurities are removed by a ceramic filter or the like before the purification treatment of the present invention. There is a need.
[0014]
Although a detailed removal mechanism for purifying crude BHET or the like is not known in the present invention, it has been found that the colorant contained in the crude BHET or the like is hardly adsorbed by the ion exchange resin and is adsorbed by activated carbon. Examples of the activated carbon used include coal-based activated carbon and wood-based activated carbon. Of these activated carbons, wood-based activated carbon is preferable in terms of the colorant removal effect and the strength in heat regeneration.
[0015]
In addition, the present inventors have found that impurity ions contained in crude BHET and the like contain both a cation component and an anion component. In order to remove these impurity ions, it was found that crude BHET and the like can be removed by heating and dissolving in a solvent at 40 to 120 ° C., preferably 60 to 100 ° C., and then passing through an anion exchange resin and a cation exchange resin. It was.
[0016]
A liquid passing temperature of less than 40 ° C. is not preferable because there is a portion that is not dissolved although it depends on the concentration of BHET or the like. Moreover, when exceeding 140 degreeC, since the service life of an ion exchange resin may become short, it is unpreferable.
[0017]
When the liquid passing temperature is 70 ° C. or higher, it is preferable to use a weakly basic anion exchange resin since the service life of the strongly basic anion exchange resin is shortened.
[0018]
Crude BHET and the like are preferably processed by dissolving in a solvent by heating, and examples of the solvent to be used include ethylene glycol used for solvolysis of methanol and PET.
[0019]
The ion exchange resin may be filled and used by a conventionally known method, and examples thereof include a multi-column type, a mixed bed type, and a laminated type. In particular, when it is desired to increase the purity, a mixed bed tower type is preferable.
[0020]
Either treatment with activated carbon or ion exchange resin has no problem in either case, but depending on the degree of purification of activated carbon, there is an elution of oxides due to the liquid passing through, so treatment with ion exchange resin is preferably performed after activated carbon treatment. It is preferable.
[0021]
【Example】
The crude BHET solution used in the examples and comparative examples is a solution after filtration obtained in the process of chemically recycling the PET bottle, and the composition is 18% by weight of BHET , 81% by weight of ethylene glycol, and 1% by weight of water. is there.
[0022]
For the crude BHET solution and the treatment liquid, the electric conductivity at 60 ° C., the color determination by visual observation, and the absorbance using a 10 mm cell were measured. The results are shown in Table 1.
Example 2
The crude BHET solution was passed through an activated carbon layer filled with 100 ml of wood activated carbon (manufactured by Nimura Chemical Co., Ltd., “Taiko SGA”) at a temperature of 80 ° C. and a flow rate of 250 ml / hr. 25 ml of “Amberlite IR120B” → 25 ml of weakly basic anion exchange resin “Amberlite IRA96SB”).
[0023]
The electrical conductivity, color determination, and absorbance of the treatment liquid were measured according to Example 1, and the results are shown in Table 1.
Comparative Example 1
The crude BHET solution was passed through an activated carbon layer filled with 100 ml of wood activated carbon (manufactured by Nimura Chemical Co., Ltd., “Taiko SGA”) at a temperature of 80 ° C. and a flow rate of 250 ml / hr.
[0024]
The electrical conductivity, color determination, and absorbance of the treatment liquid were measured according to Example 1, and the results are shown in Table 1.
Comparative Example 2
The crude BHET solution was passed through a mixed bed type ion exchange resin layer (25 ml of “Amberlite IR-402B” +25 ml of “Amberlite IR-120B”) at 60 ° C. and a flow rate of 250 ml / hr.
[0025]
The electrical conductivity, color determination, and absorbance of the treatment liquid were measured according to Example 1, and the results are shown in Table 1.
[0026]
[Table 1]

[0027]
As is clear from the results shown in Table 1, the purification method of Comparative Example 1 using activated carbon treatment alone has high conductivity because impurity ions cannot be removed, and the purification method of Comparative Example 2 using ion exchange resin alone is colored. The agent is not adsorbed and the color remains in the processing solution. On the other hand, the impurity ions and the colorant are removed from the treatment liquids of Examples 1 and 2 subjected to the activated carbon treatment and the ion exchange resin treatment.
[0028]
【The invention's effect】
The crude BHET like by purification treatment in combination with activated carbon and ion exchange resin, a colorant contained in the crude BHET and the like, it is possible to effectively remove the impurity ions. Purified BHET or the like can be used as a raw material monomer for recycled PET or the like.

Claims (2)

In a method for purifying crude bishydroxyethyl terephthalate or crude bishydroxybutyl terephthalate obtained by solvolysis of waste polyethylene terephthalate or waste polybutylene terephthalate with activated carbon and an ion exchange resin , the liquid passing temperature is 70 ° C. or higher. A method for purifying bishydroxyalkyl terephthalate, wherein the ion exchange resin is a weakly basic anion exchange resin and a cation exchange resin, and the treatment with activated carbon is performed after treatment with activated carbon . The purification method according to claim 1 , wherein the activated carbon is a wood-based activated carbon.