JPH08259728A - Production of aromatic dicarboxylic acid and alkylene glycol - Google Patents

Abstract

PURPOSE: To produce an aromatic dicarboxylic acid of excellent hue economically profitably from polyester scraps. CONSTITUTION: A thermoplastic polyester resin composition containing a small amount of a chlorine-containing resin is hydrolyzed in the presence of 0.01-10wt.%, based on the composition, basic substance to form an aromatic dicarboxylic acid and/or an alkylene glycol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION In the present invention, the main component is, for example, polyethylene terephthalate (abbreviation "PET"), polybutylene terephthalate (abbreviation "PBT") or polyethylene naphthalene dicarboxylate (abbreviation "PE").
N ") is a thermoplastic polyester having repeating units derived from an aromatic dicarboxylic acid, and the thermoplastic polyester produces an aromatic dicarboxylic acid and an alkylene glycol from a resin composition containing a small amount of a chlorine-containing resin. Regarding the method. In particular, the present invention relates to a method for industrially advantageously recovering aromatic dicarboxylic acid and alkylene glycol from waste thermoplastic polyester.

[0002]

2. Description of the Related Art A method for producing an aromatic dicarboxylic acid by hydrolyzing a thermoplastic polyester is known (see, for example, Japanese Patent Publication No. 32-8068). However, in such a publication, hydrolysis is performed by simply adding water and heating without adding a basic substance or the like to the thermoplastic polyester.

Further, as a method for producing purified terephthalic acid from a crude aromatic dicarboxylic acid containing a foreign substance, the crude aromatic dicarboxylic acid is changed to a water-soluble amine salt, the foreign substance is filtered off, and then the amine salt is decomposed. There is a known method (Japanese Patent Laid-Open No. 6-293696).

On the other hand, there is also known a method of producing an aromatic dicarboxylic acid by hydrolyzing in the presence of a stoichiometric amount of a base, removing foreign matters by filtration, and then neutralizing with an acid (USP.
5,254,666).

However, in the method for producing an aromatic dicarboxylic acid from a thermoplastic polyester described in JP-B-32-8068, a highly pure thermoplastic polyester containing substantially no impurities is used. .

However, such a technique for producing an aromatic dicarboxylic acid (recovery technique) is a technique for regenerating an aromatic dicarboxylic acid from a thermoplastic polyester that has been once used, and the recovered thermoplastic polyester has properties. Often contains chlorine-containing resin similar to that of. That is, as described above, the chlorine-containing resin (for example, polyvinyl chloride (abbreviation “PVC”), polyvinylidene chloride (abbreviation “P”)
A thermoplastic polyester resin composition containing a small amount of chlorine-containing polyalkene such as VDC ") is hydrolyzed by simply adding water as described in JP-B-32-8068 to obtain an aromatic compound. Dicarboxylic acids are often colored by hydrogen chloride generated from chlorine-containing polyalkenes, and the recovery of ethylene glycol is low. Such a colored aromatic dicarboxylic acid cannot be reused as a polyester raw material unless it is sufficiently purified.

Further, in the method described in the above-mentioned US Pat. No. 5,254,666, since the stoichiometric amount or excess of the base is used for the hydrolysis, the aromatic carboxylic acid salt produced is converted into an aromatic carboxylic acid. In order to recover the acid, it is necessary to neutralize it with an equivalent amount of acid, which raises the problem of high raw material costs.

[0008]

When the thermoplastic polyester resin composition containing a small amount of chlorine-containing resin as described above is hydrolyzed by the method described in, for example, JP-B-32-8068, it is recovered. Aromatic dicarboxylic acids have the drawbacks that they are markedly colored and are difficult to purify, and the recovery of ethylene glycol is reduced.

As described above, the method described in Japanese Examined Patent Publication No. 32-8068 is sufficiently meaningful as a method for recovering an aromatic dicarboxylic acid from pure thermoplastic polyester, but a small amount of chlorine-containing resin is mixed. There is room for improvement as a method for industrially recovering the aromatic dicarboxylic acid from the thermoplastic polyester resin composition.

On the other hand, the method described in US Pat. No. 5,254,666, which hydrolyzes in the presence of a stoichiometric amount of base, has the disadvantage of requiring an equivalent amount of acid to neutralize the aromatic dicarboxylic acid salt. As an industrial method, there is room for improvement.

[0011]

An object of the present invention is to produce an aromatic dicarboxylic acid and / or alkylene glycol having a good hue from a resin composition containing a thermoplastic polyester as a main component and a small amount of chlorine-containing resin mixed in the thermoplastic polyester. The object is to provide a method for industrially recovering

[0012]

A method for producing an aromatic dicarboxylic acid and an alkylene glycol, which is a [basic constitution] of the present invention, is a thermoplastic polyester resin composition containing a small amount of a chlorine-containing resin. For 0.0
It is characterized by being hydrolyzed to produce an aromatic dicarboxylic acid and / or alkylene glycol in the presence of a basic substance in an amount of 1 to 10% by weight.

That is, according to the method of the present invention, aromatic dicarboxylic acid and / or alkylene glycol can be recovered in high yield from a thermoplastic polyester containing a small amount of chlorine-containing resin. Moreover, although the chlorine-containing resin is mixed in the raw material, the obtained aromatic dicarboxylic acid has no color and is excellent in hue.

Although the present invention has the above basic structure, it is preferable that the present invention is constituted by each requirement defined in the following "improved structure 1" to "improved structure 5". [Improved constitution 1] The method according to [basic constitution], in which the basic substance is added in an amount necessary for capturing hydrogen chloride generated from the chlorine-containing resin.

[Improved Structure 2] The method according to [Basic Structure], wherein the chlorine-containing resin includes a chlorine-containing polyalkene, and the chlorine-containing polyalkene is polyvinyl chloride and / or polyvinylidene chloride.

[Improved Structure 3] The method according to [Basic Structure] or [Improved Structure 2], wherein the content of the chlorine-containing polyalkene in the resin composition is 10% by weight or less. [Improved Configuration 4] The basic substance is an alkali metal hydroxide, an alkali metal carbonate, an alkali metal hydrogen carbonate, an alkali metal carboxylate, an alkali metal phosphate, or an alkaline earth metal water. The method according to [basic constitution], which is one or more compounds selected from oxides, alkaline earth metal carbonates, alkaline earth metal carboxylates, alkaline earth metal phosphates and ammonia.

[Improved Structure 5] The hydrolysis temperature is 200 to
Characterized by being in the range of 300 ° C [Basic configuration]
The method described in.

[0018]

DETAILED DESCRIPTION OF THE INVENTION Next, the method for producing the aromatic dicarboxylic acid and the alkylene glycol of the present invention will be specifically described.

The present inventor has studied a method for obtaining an aromatic dicarboxylic acid with little coloring from a thermoplastic polyester resin composition containing a small amount of a chlorine-containing resin, and as a result, hydrolysis of the thermoplastic polyester was carried out at a high yield. Not only does it proceed, but the chlorine-containing resin is also decomposed during this hydrolysis reaction, and the generated hydrogen chloride causes the coloring of the aromatic dicarboxylic acid produced by hydrolysis, and also the alkylene glycol We have obtained the knowledge that this is the cause of the decrease in yield. Therefore, if the generated hydrogen chloride is completely trapped when the thermoplastic polyester resin mixed with the chlorine-containing resin is hydrolyzed, the coloring of the aromatic dicarboxylic acid obtained is reduced, and the yield of alkylene glycol is reduced. Can be improved.

Further, the recovered aromatic dicarboxylic acid thus obtained is dispersed or dissolved in water and purified by a conventional purification method such as decolorization treatment or hydrogenation treatment, whereby it can be industrially used as a polyester raw material. The grade can be raised to the level.

The recovered alkylene glycol can also be made into a grade equivalent to a commercially available product by subjecting it to purification treatment such as activated carbon treatment, hydrogenation treatment and distillation. As described above, according to the method of the present invention, the thermoplastic polyester in which a small amount of chlorine-containing resin is mixed can be hydrolyzed, and the aromatic dicarboxylic acid and the alkylene glycol can be recovered and reused, thus wasting resources. This method is extremely useful industrially in view of cost reduction as well as suppression of the above.

The method of the present invention will be specifically described below.
The thermoplastic polyester used in the present invention is a resin having a repeating unit derived from an aromatic dicarboxylic acid, and a repeating unit derived from an alkylene glycol, usually an aromatic dicarboxylic acid or a derivative thereof, and an alkylene glycol or a derivative thereof. Is formed by polycondensation of

Here, the repeating unit derived from an aromatic dicarboxylic acid is derived from, for example, terephthalic acid, isophthalic acid, alkyl-substituted products thereof, naphthalenedicarboxylic acid and diphenyldicarboxylic acid.

The repeating unit derived from alkylene glycol is derived from ethylene glycol, ethylene oxide (also known as "ethylene oxide"), propylene glycol, propylene oxide and the like.

The thermoplastic polyester having a repeating unit as described above is a polyester having a repeating unit derived from an aromatic dicarboxylic acid and an alkylene glycol, and specific examples thereof include polyethylene terephthalate (PET) and polybutylene terephthalate. (PB
T), polyethylene naphthalene dicarboxylate (P
EN).

In the method of the present invention, the above-mentioned thermoplastic polyester is used as a raw material, and this thermoplastic polyester contains a small amount of chlorine-containing resin. That is, for example, there are a great many types of recovery containers, and it is extremely difficult to select only thermoplastic polyester from such various types of molded articles. It is fully expected that resin molded products (bottles, labels, etc.) will be mixed in, and the recovered thermoplastic polyester molded product actually contains 10% by weight or less, often 1% by weight or less of chlorine. Resin is mixed.

Here, the chlorine-containing resin mixed in the thermoplastic polyester is usually a chlorine-containing polyalkene, and specific examples of the chlorine-containing polyalkene include polyvinyl chloride and polyvinylidene chloride. .

In addition to the chlorine-containing resin as described above, the thermoplastic polyester used as a raw material in the present invention may contain a resin or coating material which is not easily hydrolyzed. Non-hydrolyzable resins such as polyethylene, polypropylene and polystyrene,
Examples include metals such as aluminum, coating materials such as iron oxide, glass, and paper.

As the basic substance used in the hydrolysis in the present invention, a compound capable of reacting with hydrogen chloride generated from the chlorine-containing resin to form a water-soluble salt is used. As the basic substance, an alkali metal hydroxide, an alkaline earth metal hydroxide and ammonia can be used, and also an alkali metal or alkaline earth metal weak acid salt can be used.

That is, in the present invention, as the basic substance, alkali metal hydroxides, alkali metal carbonates, alkali metal hydrogen carbonates, alkyl metal carboxylates, alkali metal phosphates, and alkaline earths are used. Metal hydroxides,
A compound of an alkaline earth metal carbonate, an alkaline earth metal carboxylate, an alkaline earth metal phosphate and ammonia, or a combination of these compounds can be used.

Specific examples of such basic substances include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, Magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium acetate, sodium acetate, potassium acetate, magnesium acetate, calcium acetate, trisodium phosphate, tripotassium phosphate, disodium hydrogen phosphate ,
Examples thereof include dipotassium hydrogen phosphate and ammonia. Among these, any one of sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, calcium carbonate, sodium hydrogen carbonate, sodium acetate, trisodium phosphate, disodium hydrogen phosphate or ammonia, or It is preferable to use these compounds in combination.

The basic substance as described above includes the amount of chlorine-containing resin mixed in the thermoplastic polyester as a raw material, the chlorine content in the chlorine-containing resin, the stability of the chlorine-containing resin, the heating temperature, The amount of basic substance used depends on the molecular weight of the substance. That is, these basic substances are used in an amount within a range sufficient to trap hydrogen chloride generated from the chlorine-containing resin during the hydrolysis reaction. Normally, the chlorine-containing resin is 1 part in the thermoplastic polyester.
When the thermoplastic polyester containing 0% by weight or less and containing the chlorine-containing resin in such an amount is used, a base is added to the thermoplastic polyester containing the chlorine-containing resin. It is necessary to add the active substance in an amount within the range of 0.01 to 10% by weight, and it is preferable to add it in an amount within the range of 0.05 to 5% by weight. When the amount of the basic substance is too large, it reacts with the aromatic dicarboxylic acid to form a salt, so that the recovery rate of the aromatic dicarboxylic acid decreases. On the other hand, if the amount is too small, the hydrogen chloride generated from the chlorine-containing resin will be insufficiently captured, the aromatic dicarboxylic acid will be colored, and the recovery rate of alkylene glycol will decrease.

If a basic substance is used in excess of the amount for trapping the generated hydrogen chloride, the production rate of the aromatic dicarboxylic acid salt is increased, and the aromatic dicarboxylic acid free from the aromatic dicarboxylic acid salt thus generated. It is not preferable because the acid is needed to recover the acid.

The hydrolysis reaction in the present invention is usually carried out in the above-mentioned amount of the basic substance, the thermoplastic polyester in which the chlorine-containing resin is mixed, and the polyester.
This is done by heating a mixture with more than double the amount of water. Further, this hydrolysis reaction is preferably carried out under the condition that the raw material and the product are not oxidized, for example, in a non-oxidizing atmosphere or an inert gas atmosphere. This hydrolysis reaction can be carried out under normal pressure or under pressure.

The heating temperature is usually 200 ° C. to 30 ° C.
The temperature is 0 ° C, preferably 220 to 260 ° C. The reaction time at such a temperature is usually 0.1 to 5 hours, preferably 0.5 to 2 hours. This hydrolysis reaction is usually performed with stirring.

The aromatic dicarboxylic acid obtained by hydrolysis as described above is usually slightly soluble in water, although it depends on the amount of water. To deposit. On the other hand, the salt formed by the reaction of hydrogen chloride with a basic substance is dissolved in an aqueous medium, and thus the aromatic dicarboxylic acid can be collected as crystals by cooling the reaction mixture and then filtering. The filtrate contains a salt formed by the reaction of alkylene glycol and hydrogen chloride with a basic substance.

The crystals collected by filtration may contain decomposed products of chlorine-containing resin, other resins, etc., so that, if necessary, after separating these impurities by washing, extraction, recrystallization, filtration, etc., The aromatic dicarboxylic acid can be obtained by drying.

The alkylene glycol contained in the filtrate can be separated by, for example, distillation, extraction and removal of the extraction solvent. Thus, in the method of the present invention, the aromatic dicarboxylic acid is directly recovered from the thermoplastic polyester mixed with the chlorine-containing resin without forming a salt. And, the thermoplastic polyester used in the present invention is high without being affected by hydrogen chloride or the like generated from the chlorine-containing resin, even though the chlorine-containing resin such as polyvinyl chloride is mixed. The aromatic dicarboxylic acid can be recovered with a recovery rate. Moreover,
Coloring of the recovered aromatic dicarboxylic acid is small.

The same applies to alkylene glycol.

[0040]

The present invention will be described below with reference to examples.
The present invention is not limited to these examples. A reference example is also presented.

[0041]

Example 1 Recycled PE containing a small amount of polyvinyl chloride, etc.
T-flakes (made by With PET Bottle Recycle) 15
0 g, sodium hydroxide 1 g (25 mmol) and water 450 g
PET in an autoclave at 240 ° C for 2 hours with PET.
Was hydrolyzed.

The recycled PET flakes contained 40 ppm or less of polyvinyl chloride and 150 g of the flakes.
The amount of hydrogen chloride which is predicted to be generated by hydrolyzing the above at 2 ° C. for 2 hours is 0.1 mmol or less.

After cooling the reaction mixture to room temperature, the precipitate was filtered, washed with water and dried to give crude terephthalic acid 12
3.9 g were obtained. The content of terephthalic acid in the obtained terephthalic acid was determined by high performance liquid chromatography to be 95.2%. It was also found that the content of monohydroxyethyl ester of terephthalic acid was 3.8%.

The alkali transmittance (7.5 g of sample terephthalic acid was dissolved in 50 ml of 2N KOH aqueous solution and measured at a wavelength of 340 nm using a sample solution filtered through a chromatodisc), and the alkali transmittance was 66. %Met.

The recovery rate of terephthalic acid calculated based on the diethylene glycol concentration in the regenerated PET flakes being 1.4% (2.6 mol%) was 91.5%. In addition, when ethylene glycol in the filtrate and the washing liquid was quantified by gas chromatography analysis, the recovery rate of ethylene glycol was 9
It was 1.7%.

[0046]

[Comparative Example 1] The procedure of Example 1 was repeated except that sodium hydroxide was not added. The alkali permeability was 53% and the terephthalic acid recovery rate was 93.5%.
Met. The recovery rate of ethylene glycol is 88.3%.
Met.

[0047]

Examples 2 to 6 Aromatic dicarboxylic acids were obtained in the same manner as in Example 1 except that the basic substances shown in Table 1 were used instead of the sodium hydroxide in Example 1.

As in Example 1, the obtained aromatic dicarboxylic acid was examined for alkali permeability, terephthalic acid recovery rate and ethylene glycol recovery rate, and the results are shown in Table 1.

[0049]

[Table 1]

[0050]

Example 7 150 g of recycled PET flakes and a commercial polyvinyl chloride bottle were crushed, washed with water, and then dried 1
6.7 g (predicted amount of hydrogen chloride generated: 0.27 mol),
Sodium hydroxide 10.7 g (0.27 mol) and water 45
Stir 0 g in an autoclave at 240 ° C. for 2 hours to obtain P
The ET was hydrolyzed. After cooling the reaction mixture to room temperature, the precipitate was filtered, washed with water and dried to obtain 132.6 g of crude terephthalic acid.

This contained 7.0 g of a polyvinyl chloride decomposition product, and the terephthalic acid content in the crude terephthalic acid excluding this was 94.8 according to high performance liquid chromatography analysis.
%, And it was found that the content of monohydroxyethyl ester was 3.4%. The alkali transmission rate of terephthalic acid was 60%, and the recovery rate was 93.3%.

The ethylene glycol recovery rate is 87.2.
%Met.

[0053]

Comparative Example 2 The same procedure as in Example 7 was carried out except that sodium hydroxide was not added. The alkali permeability was 10% and the terephthalic acid recovery rate was 98.3%.
And the ethylene glycol recovery was 24.7%.

[0054]

According to the method of the present invention, a thermoplastic polyester resin composition containing a small amount of a chlorine-containing resin, that is, a thermoplastic polyester waste, is not affected by hydrogen chloride generated from the chlorine-containing resin. The aromatic dicarboxylic acid and / or alkylene glycol having a good hue can be recovered in high yield.

Moreover, in the method of the present invention, since the basic substance is used only in an amount necessary for capturing the hydrogen chloride generated from the chlorine-containing resin, it is not necessary to recover the aromatic dicarboxylic acid. The raw material cost can be reduced and the recovery cost of the aromatic dicarboxylic acid and / or alkylene glycol can be reduced.

In addition, as in the present invention, the hydrogen chloride and the like generated from the chlorine-containing resin is reliably captured by the basic substance, so that the hydrolysis device is less corroded.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08G 63/88 NLK C08G 63/88 NLK C08K 3/20 KJR C08K 3/20 KJR C08L 27/04 LFK C08L 27/04 LFK 67/02 LNZ 67/02 LNZ // B29K 67:00 105: 26

Claims (6)

[Claims] 1. A thermoplastic polyester resin composition containing a small amount of chlorine-containing resin is added to the resin composition in an amount of 0.
A method of producing an aromatic dicarboxylic acid and / or alkylene glycol by hydrolysis in the presence of a basic substance in an amount of 01 to 10% by weight. 2. The amount of basic substance is 0.01 to 10% by weight.
2. The method according to claim 1, wherein the amount of hydrogen chloride is within the range of 1 and is necessary to capture hydrogen chloride generated from the chlorine-containing resin. 3. The method according to claim 1, wherein the chlorine-containing resin includes a chlorine-containing polyalkene, and the chlorine-containing polyalkene is polyvinyl chloride and / or polyvinylidene chloride. 4. The method according to claim 1 or 3, wherein the content of the chlorine-containing polyalkene in the resin composition is 10% by weight or less. 5. The basic substance is an alkali metal hydroxide, an alkali metal carbonate, an alkali metal hydrogen carbonate, an alkali metal carboxylate, an alkali metal phosphate, or an alkaline earth metal water. 2. One or more compounds selected from oxides, alkaline earth metal carbonates, alkaline earth metal carboxylates, alkaline earth metal phosphates and ammonia. The method described. 6. The method according to any one of claims 1 to 5, wherein the hydrolysis temperature is in the range of 200 to 300 ° C.