JP2001322966A - Method for recovering dimethyl naphthalenedicarboxylate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering dimethyl naphthalenedicarboxylate of high purity at high yield from polyester waste containing polymers having alkylene naphthalenedicarboxylate unit. SOLUTION: This method comprises recovering dimethyl naphthalenedicarboxylate from a reaction product obtained by methanolysis of polymers having alkylene naphthalenedicarboxylate unit and/or its alkylene glycol depolymerization product; wherein the methanolysis is performed in the condition using methanol containing <=0.3 wt.% water, using 2-25 times methanol based on the weight of the polymers having an alkylene naphthalenedicarboxylate unit and/or its alkylene glycol depolymerization product and dissolving >=50 wt.% dimethyl naphthalenedicarboxylate in the reaction liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering a monomer from a polymer, and more particularly to a method for recovering dimethyl naphthalenedicarboxylate from a polyester waste containing a polymer containing alkylene naphthalenedicarboxylate units with high purity and high purity. The yield relates to the recovery method.

[0002]

2. Description of the Related Art Polyethylene naphthalene dicarboxylate (hereinafter sometimes abbreviated as PEN) has better heat resistance and mechanical properties than polyethylene terephthalate (hereinafter sometimes abbreviated as PET). , Fibers, films, and plastics are attracting attention as high-performance materials. However, 2,6-naphthalenedicarboxylic acid and / or its derivative as a raw material is expensive, and PEN is used in the polymerization process or in the form of a filament. In the process of forming into a film, defective products and debris are liable to be generated. Therefore, these defective products and debris, and furthermore, products after use (hereinafter, collectively referred to simply as waste polyester) Is economically preferable to collect and reuse, and it is necessary from the viewpoint of global environmental measures.

However, dyes, flame retardants, general refuse, and other plastics are mixed in these collected waste polyesters, and it is often difficult to melt-mold and reuse them as they are. It is necessary to separate and recover 2,6-naphthalenedicarboxylic acid and / or its derivative, which is a raw material of the polyester, from the polyester waste in the form of a monomer. In addition, in order to maintain the high performance of PEN, the purity of the recovered product is required. Requires 99.8% by weight or more, and a method of separating and recovering high-purity 2,6-naphthalenedicarboxylic acid and / or a derivative thereof in the form of a monomer has been required.

In general, methods for recovering raw materials from polyesters such as PET and PEN include a method of directly depolymerizing polyester with methanol and a method of depolymerizing polyester with ethylene glycol followed by transesterification with methanol. (Japanese Patent Laid-Open Publication No. Hei 3-504379, Japanese Patent Laid-Open Publication No. Hei 10-218984, etc.) are known.

However, the physical properties of PEN and dimethyl naphthalenedicarboxylate (hereinafter sometimes abbreviated as NDCE) are remarkably different from those of PET and dimethyl terephthalate (hereinafter sometimes abbreviated as DMT). Is different. Therefore, DM from PET
The experience gained from T recovery cannot be directly applied to the recovery of NDCE from PEN, and the physical properties of the polyester must be considered in determining suitable recovery conditions for PEN. For example, NDCE generally forms smaller crystals than DMT, and operations such as filtration and washing are difficult. In addition, since PEN and NDCE contain a naphthalene ring, they have the characteristic that even a small amount of impurities significantly deteriorates the hue, and a recovery method for solving these problems has been required.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to obtain dimethyl naphthalenedicarboxylate from polyester waste containing a polymer containing alkylene naphthalenedicarboxylate units. To provide a high-purity and high-yield recovery method.

[0007]

DISCLOSURE OF THE INVENTION In view of the above-mentioned prior art, the present inventors have obtained a high-quality dimethyl naphthalenedicarboxylate from a polymer containing a polyethylene naphthalenedicarboxylate unit and / or an alkylene glycol depolymerized product thereof. The present inventors have made intensive studies on a method of recovering the compound in a high yield, and have completed the present invention.

That is, an object of the present invention is to recover dimethyl naphthalenedicarboxylate from a polymer containing an alkylene naphthalenedicarboxylate unit and / or a reaction product obtained by subjecting an alkylene glycol depolymerized product to methanolysis. A water content of 0 in methanolysis.
Methanol of 3% by weight or less is used, and the amount thereof is 2 to 25 times based on the weight of the polymer containing alkylene naphthalenedicarboxylate and / or the alkylene glycol depolymerized product, and is further produced by the methanolysis. This can be achieved by a method for recovering dimethyl naphthalenedicarboxylate, wherein the methanolysis is carried out under the condition that 50% or more of dimethyl naphthalenedicarboxylate is dissolved in the reaction solution.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION
Methanol having a water content of 0.3% by weight or less is used, and the amount thereof is 2 to 25 times based on the weight of the polymer containing alkylene naphthalenedicarboxylate and / or the alkylene glycol depolymerized product. It is necessary that 50% or more of the dimethyl naphthalenedicarboxylate formed by methanolysis be dissolved in methanol.

[0010] If the reaction is carried out under a reaction condition in which 50% or more of the dimethyl naphthalenedicarboxylate formed in the methanolysis is dissolved in methanol, crystals having good operability can be obtained upon cooling. Further, it is particularly preferable to carry out the reaction under the reaction conditions in which the entire amount of dimethyl naphthalenedicarboxylate to be completely dissolved in methanol can also obtain the effect of recrystallization.

In order to set the reaction conditions so as to dissolve as described above, the amount of methanol and the reaction temperature may be appropriately selected and set, but the reaction temperature may be set at 80 to 280 ° C. The temperature is particularly preferably 120 to 190 ° C.

When the methanolysis is carried out at a temperature of 240 ° C. or lower, a catalyst may be used to promote the methanolysis. Examples of the catalyst include alkali metals or alkaline earth metals, hydroxides, oxides and the like. Carbonates and acetates; zinc, tin, titanium, antimony, manganese, cobalt and lead oxides and acetates; and the like, and these compounds may be used alone or in combination of two or more.

The amount of the catalyst to be added to the reaction system is preferably 0.02 parts by weight or less per 1 part by weight of the polymer containing alkylene naphthalenedicarboxylate units and / or its alkylene glycol depolymerized product. ,
If the amount of the catalyst used is reduced, the amount of by-produced salt can be reduced in proportion to this. The amount of the catalyst to be added to the reaction system may be appropriately set based on the set reaction temperature and reaction time.

Further, the amount of methanol used in this reaction must be 2 to 25 times based on the weight of the polymer containing alkylene naphthalenedicarboxylate units and / or the alkylene glycol depolymerized product thereof. Preferably it is 4 to 10 parts by weight. When in this range, the equilibrium of the transesterification reaction largely shifts to the dimethyl naphthalenedicarboxylate generation side, and the amount of dimethyl naphthalenedicarboxylate dissolved in methanol when cooled during the recrystallization operation is small, so that high-purity naphthalenedicarboxylic acid Dimethyl crystals can be obtained in high yield.

In the recovery method of the present invention, the methanol used in methanolysis needs to have a water content of 0.3% by weight or less, and it is more preferable that the water content approaches zero. If water is contained, it has adverse effects such as by-producing a substance that inhibits crystal growth during recrystallization and inhibiting the action of the catalyst when performing methanolysis using a catalyst. The methanol can be recycled and reused, but in this case, the water content must be 0.3% by weight or less as in the above case. When dimethyl naphthalenedicarboxylate is recovered from a polymer containing an alkylene naphthalenedicarboxylate unit, methanol is used to remove various impurities such as water and alkylene glycol by distilling and purifying unreacted components of methanol used in the reaction. It is efficient to reuse. Among these impurities, in particular, when water generated by a side reaction or the like is mixed into methanol, by-producing a substance that inhibits crystal growth during recrystallization, or when performing methanolysis using a catalyst, the catalyst may be used. By inhibiting the action of NDCE
Crystals become finer, and operations such as washing and solid-liquid separation become difficult, causing a very troublesome problem that it is difficult to remove impurities transferred to the filtrate side. To solve this problem, it is effective to increase the amount of the catalyst, but as described above, increasing the amount of the catalyst is not preferable because it increases the generation of salts.

In order to purify high-purity NDCE, the product obtained by methanolysis (hereinafter referred to as crude NDCE)
May be abbreviated as ) May be further distilled, but NDCE having a purity of 99.8 wt% or more, which is the object of the present invention,
In order to obtain, it is necessary to reduce the liquid content of the cake at the stage of solid-liquid separation of the crude NDCE and to remove impurities present in the accompanying filtrate from the cake. If the content is 3 wt% or less, the generated crude NDCE
Since the crystals do not become fine, the liquid content can be easily reduced.

The crude N obtained in this way
From the DCE cake, 9
NDCE with a purity of 9.8 wt% or more can be easily obtained in a high yield of 85% or more. In addition, coarse N
If a distillation operation is performed after recrystallizing the DCE cake, it is possible to obtain high-purity NDCE, but there is a drawback that equipment investment is increased.

The recovery method of the present invention is not limited to a batch method. For example, a polymer containing an alkylene naphthalene dicarboxylate unit and an alkylene glycol are continuously supplied to a depolymerization tank while the polymer is depolymerized by the alkylene glycol. The obtained solution is continuously supplied to the transesterification reaction tank together with methanol, and the methanol solution in which dimethyl naphthalenedicarboxylate is dissolved is continuously taken out of the system and cooled, whereby crystals of dimethyl naphthalenedicarboxylate are continuously produced. After obtaining, a purification operation such as distillation may be added.

In the present invention, examples of the alkylene naphthalenedicarboxylate unit include ethylene naphthalenedicarboxylate, butylene naphthalenedicarboxylate, and the like. Usually, ethylene naphthalenedicarboxylate is used.

As the alkylene glycol used in the present invention, for example, ethylene glycol, diethylene glycol and the like can be mentioned. Among them, it is preferable to use ethylene glycol which is produced as a by-product when repolymerized from recycled materials. .

[0021]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the present invention. The concentration of dimethyl naphthalenedicarboxylate described in the examples was determined by using a high-performance liquid chromatograph (manufactured by Hitachi, Ltd .: column "Recrosssphere 100").
Using RP-18 "), the rate of dissolution of the produced NDCE in the solution after the methanolysis reaction was determined in advance by measuring the amount of NDCE dissolved in 100 g of methanol (130 ° C = 20 g, 140 ° C = 30 g). 180 ° C = 3
0 g or more).

Example 1 180 g of ethylene glycol was added to 180 g of PEN, and the mixture was reacted in an autoclave made of glass with a stirrer at 260 ° C., without a catalyst and in a closed system (reaction pressure: about 0.6 MPa) for 60 minutes. . After the completion of the reaction, 157.
5 g were distilled off. Next, 0.54 g of sodium carbonate and 1080 g of methanol (reagent product: water content <0.1 wt%) as a catalyst were added thereto, and the mixture was placed in an autoclave with a stirrer at 130 ° C. under closed system conditions (reaction pressure: 0). .7M
Pa) for 60 minutes. After the reaction, 100% of the produced NDCE was dissolved in the solution after the methanolysis reaction. After the reaction was completed, the reaction product was allowed to cool to room temperature, and then the reaction product was taken out. This reaction product contains large crystals that are easy to separate,
This was subjected to solid-liquid separation by filtration to obtain a cake (A) and a filtrate (B). In the methanolysis of the second batch and subsequent batches of these series of operations, methanol obtained by distilling the filtrate (B) of the previous batch and methanol as a reagent is added to methanol (water content: 0.1 to 0.3 wt%). )
5 batches were performed.

Next, the cake (A) of 5 batches obtained was mixed, heated and distilled under the conditions of a pressure of 10 mmHg, a theoretical plate number of 20 and no reflux, and as a result, a seriousness of 99.9 was obtained.
804.6 g of a 5% by weight NDCE crystal was obtained (yield = 88.2%). In this experiment, although 38 g could not be distilled off and remained in the distillation apparatus due to the scale of the experimental equipment, 50 wt% or more of this substance was NDCE.
It is expected that the yield will be further improved by increasing the equipment scale.

Example 2 To 180 g of PEN was added 45 g of ethylene glycol, and the mixture was placed in an autoclave equipped with a stirrer at 260 ° C. in the absence of a catalyst in a closed system (reaction pressure: about 0.
6 MPa) for 60 minutes. After the completion of the reaction, 0.54 g of sodium carbonate as a catalyst and methanol 1
800 g (reagent product: water content <0.1 wt%) was added, and the mixture was reacted in an autoclave equipped with a stirrer at 130 ° C. under closed system conditions (reaction pressure: 0.7 MPa) for 60 minutes.
After the reaction, 100% of the produced NDCE was dissolved in the solution after the methanolysis reaction. After the completion of the reaction, the reaction product was allowed to cool to room temperature, and the reaction product was taken out.
This reaction product contained large crystals that were easy to separate, and this was subjected to solid-liquid separation by filtration to obtain a cake (C) and a filtrate (D). In the methanolysis of the second batch and subsequent batches of these series of operations, methanol obtained by adding the reagent product methanol to the total amount of methanol obtained by distilling the filtrate (D) of the previous batch (water content: 0.1 to
(0.3 wt%).

Next, the cake (C) of the 5 batches obtained was mixed, heated and distilled under the conditions of a pressure of 10 mmHg, a theoretical plate number of 20 and no reflux, and as a result, a purity of 99.9 was obtained.
808.2 g of a 6% by weight NDCE crystal was obtained (yield = 88.7%).

Example 3 To 200 g of PEN, 4 g of sodium carbonate and 1000 g of methanol (reagent product: water content <0.1 wt%) were added, and the mixture was sealed in an autoclave equipped with a stirrer at 180 ° C. under closed system conditions (reaction pressure: 2). .4MP
The reaction was performed for 180 minutes in a). After the reaction, 100% of the produced NDCE was dissolved in the solution after the methanolysis reaction. After the completion of the reaction, the reaction product was allowed to cool to room temperature, and the reaction product was taken out. This reaction product contained large crystals that were easy to separate, and this was subjected to solid-liquid separation by filtration to obtain cake (E) and filtrate (F). In the methanolysis of the second batch and subsequent batches of these series of operations, methanol obtained by distilling the filtrate (F) of the previous batch and methanol as a reagent is added to methanol (water content: 0.1 to 0.3 wt%). 5).

Next, the cake (E) of the 5 batches obtained was mixed, heated and distilled under the conditions of a pressure of 10 mmHg, a theoretical plate number of 20 and no reflux, and as a result, a purity of 99.9 was obtained.
859.7 g of 2 wt% NDCE crystals were obtained (yield = 85.3%).

Comparative Example 1 180 g of ethylene glycol was added to 180 g of PEN, and the mixture was reacted in an autoclave equipped with a stirrer at 260 ° C., without a catalyst and in a closed system (reaction pressure: about 0.6 MPa) for 60 minutes. After the completion of the reaction, 157.5 g of ethylene glycol and light-boiling components were distilled off. Next, 0.5% of sodium carbonate as a catalyst was added thereto.
4 g and methanol 1080 g (water content = 1.0 wt.
%) In an autoclave with a stirrer, 130 ° C.
The reaction was carried out for 60 minutes under a closed system condition (reaction pressure: 0.7 MPa). After completion of the reaction, 100
% Was dissolved in the solution after the methanolysis reaction. After the reaction was completed, the reaction product was allowed to cool to room temperature, and then the reaction product was taken out. This was subjected to solid-liquid separation by filtration to obtain a cake (G) and a filtrate (H). In the methanolysis of the second and subsequent batches of these series of operations, methanol as a reagent was added to the total amount of methanol obtained by distilling the filtrate (H) of the previous batch, and the water content was further adjusted to methanol (water content = 1.0 wt. %).

Next, the cake (G) for 5 batches obtained was mixed, heated and distilled under the conditions of a pressure of 10 mmHg, a theoretical plate number of 20 and no reflux, and as a result, a purity of 98.7 was obtained.
756.0 g of 4% by weight of NDCE crystals was obtained (yield = 77.4%).

Comparative Example 2 180 g of ethylene glycol was added to 180 g of PEN, and the mixture was reacted in an autoclave equipped with a stirrer at 260 ° C., without a catalyst and in a closed system (reaction pressure: about 0.6 MPa) for 60 minutes. After the reaction was completed, 157.5 g of ethylene glycol and light-boiling components were distilled off. Then, sodium carbonate 0.1 as a catalyst was added thereto.
54 g and methanol 360 g (reagent product: water content <
0.1 wt%) in an autoclave with a stirrer at 130 ° C under closed system conditions (reaction pressure: 0.7 MPa).
For 60 minutes. After the reaction is completed, the generated NDC
15% of E was dissolved in the solution after the methanolysis reaction. After the reaction was completed, the reaction product was allowed to cool to room temperature, and then the reaction product was taken out. This reaction product contained fine crystals, which were subjected to solid-liquid separation by filtration over time to obtain cake (I) and filtrate (J). In the methanolysis of the second batch and subsequent batches of these series of operations, methanol obtained by distilling the filtrate (J) of the previous batch and methanol as a reagent is added to methanol (water content: 0.1 to 0.3 wt%). 5).

Next, the cake (I) of 5 batches obtained was mixed, heated and distilled under the conditions of a pressure of 10 mmHg, 20 theoretical plates and no reflux, and as a result, a purity of 98.5 was obtained.
576.3 g of 2% by weight of NDCE crystals were obtained (yield = 58.2%). In this comparative example, the distillation residue was 10
Although the amount was 3.6 g and 2-3 times the amount in comparison with the other examples,
The concentration of NDCE contained therein was about 50%.

[0032]

According to the recovery method of the present invention, dimethyl naphthalenedicarboxylate can be stably recovered in high yield and high purity from polyester waste containing a polymer containing an alkylene naphthalenedicarboxylate unit. become.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuhiro Sato 77-family Kitayoshida-cho, Matsuyama-shi, Ehime Teijin Limited Matsuyama Office F-term (reference) 4F301 AA25 AB03 CA09 CA23 CA24 CA42 CA71 4H006 AA02 AC48 AC91 BA02 BA06 BA07 BA10 BA11 BA13 BA16 BA20 BA29 BA30 BA32 BC31 BC37 BC40 BD10 BJ50 KA03 4H039 CA66 CD40 CD90 CL30

Claims (5)

[Claims] 1. When recovering dimethyl naphthalenedicarboxylate from a polymer containing an alkylene naphthalenedicarboxylate unit and / or a reaction product obtained by subjecting an alkylene glycol depolymerized product to methanolysis, a water content of 0 is added to methanolysis. 0.3% by weight or less of methanol and the amount thereof is from 2 to 25 based on the weight of the polymer containing alkylene naphthalenedicarboxylate and / or its alkylene glycol depolymerized product.
A method for recovering dimethyl naphthalenedicarboxylate, characterized in that the methanolysis is carried out under the condition that 50% or more of the dimethyl naphthalenedicarboxylate formed by the methanolysis is dissolved in the reaction solution. 2. The recovery method according to claim 1, wherein the methanolysis is carried out under conditions in which the entire amount of dimethyl naphthalenedicarboxylate produced by the methanolysis is dissolved in the reaction solution. 3. The recovery method according to claim 1, wherein in the methanolysis, 0.02 times or less of a catalyst is used based on the weight of the polymer containing alkylene naphthalenedicarboxylate and / or its alkylene glycol depolymerized product. . 4. The method according to claim 1, wherein the alkylene naphthalenedicarboxylate unit is ethylene naphthalenedicarboxylate. 5. The method according to claim 1, wherein the alkylene glycol is ethylene glycol.