JPH07316280A - Method of recycling waste aromatic polycarbonate resin - Google Patents

Abstract

PURPOSE:To economically recover an aromatic dihydroxy compound and a diaryl carbonate compound which are usable as high-quality raw materials by reacting a waste aromatic polycarbonate resin with an aromatic monohydroxy compound through transesterification and treating the reaction products in a specific manner. CONSTITUTION:An aromatic polycarbonate resin is reacted with an aromatic monohydroxy compound (X) (e.g. phenol) through transesterification. A diaryl carbonate compound (e.g. diphenyl carbonate) containing the compound X is separated from the transesterification products by distillation. The compound X is added to the remaining aromatic dihydroxy compound (Y) (e.g. bisphenol A), and this mixture is heated to form an adduct of both and then cooled to crystallize the adduct. The resulting crystals are taken out and thermally melted, and the compound X is distilled off to obtain the compound Y. According to need, the compound Y and the diaryl carbonate compound are used as the raw material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for recycling waste aromatic polycarbonate resin. More specifically, the present invention relates to a method for recycling a waste aromatic polycarbonate resin, in which unnecessary aromatic polycarbonate resin is decomposed, converted into a raw material of the aromatic polycarbonate resin, and reused.

[0002]

2. Description of the Related Art Aromatic polycarbonate resins have excellent transparency, optical properties and tough physical properties, so that they are used for lenses, compact discs, building materials, automobile parts, and O.
It is an extremely high value-added material used in various applications such as chassis of A equipment, camera body, etc., and its demand is increasing more and more. When these products are no longer used, most of them are disposed of by waste, such as incineration or underground disposal.

This is not only a significant waste of resources, but the increasing waste plastics disposal has become a social problem as a global environmental problem and is becoming a subject of regulation. Therefore, the waste aromatic polycarbonate resin is partially reformed and used. However, there are problems such as a decrease in molecular weight, a decrease in physical properties, and coloring, and it is difficult to reuse a large amount. Moreover, even if it is reused, it is not essentially recycled because it is discarded after its use.

[0004]

SUMMARY OF THE INVENTION The present invention is an essential recycling method in which an aromatic dihydroxy compound, a diaryl carbonate compound or the like obtained by decomposing a waste aromatic polycarbonate resin is used again as a raw material for producing an aromatic polycarbonate resin. The purpose is to provide.

Aromatic dihydroxy compounds and diaryl carbonate compounds used as raw materials for aromatic polycarbonate resins are required to have high purity. However, the aromatic polycarbonate resin that has been once used and has become a waste not only has dirt, oil and fat stains attached to it, but also has various surface treatments and other resin In many cases, it is a mixture with and a colorant or a reinforcing material is blended. Therefore, in the reaction solution obtained by subjecting the waste aromatic polycarbonate resin to the transesterification reaction with the aromatic monohydroxy compound as it is, various impurities are mixed in addition to the active ingredient, and it is difficult to separate and purify the active ingredient. In many cases, there are problems that the decomposition reaction is difficult to proceed, and that side reactions or decomposition reactions of the decomposition reaction product obtained at the same time occur to cause deterioration of the quality and yield of the active ingredient. It was

In particular, the thermal stability of the aromatic dihydroxy compound in the reaction solution is not sufficient, and when purified by a distillation method, heat and / or impurities remaining in the reaction solution, for example, the presence of trace amounts of acid and alkali. Therefore, it is difficult to obtain an aromatic dihydroxy compound with a high yield and a high quality because it is likely to be transformed into a high boiling point component.

The inventor of the present invention has prepared a method in which an active ingredient is extracted from a reaction product obtained by heating waste aromatic polycarbonate resin together with an aromatic monohydroxy compound to form an aromatic dihydroxy compound and a diaryl carbonate compound. The present invention has been accomplished by earnestly researching a recovery method that can be economically recovered on an industrial scale without causing a problem.

[0008]

The present invention provides a method for recovering aromatic dihydroxy compounds and diaryl carbonate compounds by a transesterification reaction between a waste aromatic polycarbonate resin and an aromatic monohydroxy compound,
(A) A first step of transesterifying an aromatic polycarbonate resin and an aromatic monohydroxy compound,
(B) A second step of distilling and separating a diaryl carbonate compound containing an aromatic monohydroxy compound from the reaction product obtained in the first step, and (C) an aromatic dihydroxy compound remaining in the second step. After the hydroxy compound is added and heated to form both adducts, the crystals obtained in the third step of crystallizing and separating the adduct by cooling and (D) the third step are heated and melted to give an aroma. A method for recycling a waste aromatic polycarbonate resin comprising a fourth step of distilling off a group monohydroxy compound to obtain an aromatic dihydroxy compound.

The waste aromatic polycarbonate resin targeted by the present invention is an aromatic polycarbonate resin obtained by synthesizing a dihydric phenol and a carbonate precursor by a solution method. Non-defective products, aromatic polycarbonate resin products, etc. that have been no longer used or are no longer needed.

2,2-bis (4-hydroxyphenyl) propane (hereinafter abbreviated as bisphenol A) is usually used as the dihydric phenol which is a raw material for the aromatic polycarbonate resin. Is not limited to the aromatic polycarbonate resin of bisphenol A, but is also applicable to other aromatic polycarbonate resins of dihydric phenol.

Such waste aromatic polycarbonate resin can be applied to the method of the present invention with or without pretreatment as necessary, but pretreatment is often preferable. Any method may be adopted as the pretreatment. For example, if the waste aromatic polycarbonate resin is contaminated with dust, oils, and other contaminants, it is preferable to thoroughly clean it, and in the case of disks such as compact disks and magneto-optical disks, the front and back surfaces should be processed. It is preferable to apply after removing the processed layer, the printing layer, etc., which have been removed, and when the waste aromatic polycarbonate resin is an alloy, it is preferable to apply the aromatic polycarbonate resin component after previously separating it. In short, it is preferable to avoid mixing impurities into the decomposition reaction as much as possible. Further, it is preferable to pulverize in advance from the viewpoint of handling and reaction.

As the aromatic monohydroxy compound, various phenols can be used (hereinafter, the aromatic monohydroxy compound is abbreviated as phenols), but phenol is particularly preferable. When water is present in the decomposition reaction, the carbonate group of the resulting diaryl carbonate compound is hydrolyzed, so that the water content of phenols is 5% by weight or less, preferably 1% by weight or less, and particularly 0.5% by weight.
The following is preferable. The amount used is usually 0.8 to 1000 times the weight of the waste aromatic polycarbonate resin, preferably 1 to 100 times the weight, and 5 to 20 times the weight is particularly preferable because the phenols also serve as a solvent.

The waste aromatic polycarbonate resin is first supplied to the reaction zone of the first step. The waste aromatic polycarbonate resin supplied may be in a molten state or a solid, and may be supplied together with phenols.

The decomposition reaction by transesterification between the phenols and the aromatic polycarbonate resin in the reaction zone of the first step, when phenol is used as the phenols, is the melting point of the phenol to 300 ° C., preferably 150 to
It is preferable to carry out at 280 ° C. This decomposition reaction can also be carried out using a conventionally known catalyst. Usually, it is refluxed near the boiling point of phenol under atmospheric pressure without using a catalyst, or at high temperature and high pressure for a short time in the presence or absence of a catalyst. In the latter case, the equipment cost may be lower and the cost may be lower.

The time required for the decomposition reaction varies depending on the reaction temperature and the presence or absence of the catalyst, but it is 5 seconds to 12 seconds.
It is often 0 minutes, preferably 10 seconds to 80 minutes. Usually, the reaction under high temperature and high pressure often ends in a short time. In both cases, the conditions for the decomposition reaction are selected so as to prevent the occurrence of side reactions. This decomposition reaction can be carried out batchwise or continuously.

In the second step, the diaryl carbonate compound which is one of the active ingredients and the aromatic dihydroxy compound which is another active ingredient are separated. In the second step, the decomposition reaction product as it is, or a part of the phenols is evaporated and recovered, and then the diaryl carbonate compound is recovered by distillation.

As the distillation apparatus, an apparatus having a distillation column, an evaporator in the lower part, and a condenser and a reflux device in the upper part can be used. Any apparatus can be used as the distillation apparatus, but one having a small amount of stay and a short stay time is used for cost reduction and quality deterioration prevention. For example, when the distillation column is a packed column system, it is preferable that the packing material has the least pressure loss and high contact efficiency, and the evaporator is a thin film type.

The distillation temperature is 120 to 250 ° C., preferably 150 to 220 ° C., the pressure is 2 to 500 Torr,
It is preferably 5 to 100 Torr. The diaryl carbonate compound that has been distilled off by distillation contains phenol remaining in the decomposition reaction, and the waste polycarbonate may contain a polymerization terminator having a lower boiling point than the diaryl carbonate compound. If necessary, these phenols and the polymerization terminator are separated from the diaryl carbonate compound by a conventionally known method, for example, by distillation,
Recovered as a solid in the molten state or by cooling. Further, if desired, it may be purified by any method. The liquid containing an aromatic dihydroxy compound as a main component, which is obtained by distilling off the diaryl carbonate compound, is taken out from the lower part of the distillation column and sent to the next third step.

In the third step, another active ingredient, an aromatic dihydroxy compound, is purified. The aromatic dihydroxy compound separated in the second step often contains the high boiling impurities contained in the waste polycarbonate resin, the decomposition reaction, and the high boiling impurities generated in the second step. Therefore, in order to obtain a high-quality aromatic dihydroxy compound, phenols are added and heated to form an adduct of the aromatic dihydroxy compound and the phenol, and then cooled to crystallize and separate the adduct. The method is adopted.

With respect to 1 part by weight of the residue containing the aromatic dihydroxy compound as the main component, which was obtained from the bottom of the distillation column in the second step, 0.5 parts of phenol was added as phenol.
-10 parts by weight, preferably 1.0-5 parts by weight,
Heat to 80-200 ° C, preferably 100-160 ° C. An adduct of 1 mol of phenol is formed with respect to 1 mol of the aromatic dihydroxy compound. If the amount of phenol added is less than the above amount, the formation of the adduct will be insufficient and an aromatic dihydroxy compound of sufficient quality cannot be obtained. On the other hand, when the amount of phenol is too much, the yield of the aromatic dihydroxy compound recovered as an adduct decreases.

The solution obtained by heating as above is then cooled to 40 to 70 ° C., preferably 40 to 60 ° C. to crystallize the adduct as crystals. The crystal adduct is recovered by a conventionally known solid-liquid separation method such as filtration or centrifugation. The separated crystalline adduct is washed with phenol and sent to the next fourth step.

The mother liquor separated here is used by a conventionally known method, for example, by recovering phenol by evaporation or the like, refining it if necessary, and circulating it. The crystallization in the third step can be repeated if necessary. It can be carried out batchwise or continuously.

In the fourth step, the crystalline adduct obtained in the third step is heated and melted, the aromatic dihydroxy compound and the phenol are separated under vacuum, and the aromatic monohydroxy compound is distilled off. The temperature for separation is 160 to 250 ° C., preferably 180 to 220 ° C., in consideration of the thermal stability of the aromatic dihydroxy compound. The pressure at that time is 0.5-4
It is 0 Torr, preferably 1 to 10 Torr.

The apparatus used is preferably a thin-film type evaporator in which the amount of aromatic dihydroxy compound retained is short and the residence time is short.

The aromatic dihydroxy compound recovered as described above is taken out as a solid in a molten state or once cooled. The fourth step can be carried out batchwise or continuously.

FIG. 1 shows an example of the process of the present invention. In the figure,
PC represents polycarbonate, DPC represents diphenyl carbonate, and BPA represents bisphenol A.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, high-quality aromatic dihydroxy compounds and diaryl carbonate compounds can be economically recovered on an industrial scale. The recovered compound is recycled to the melt polymerization reaction step if necessary, and the effect produced is remarkable.

[0028]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. Parts and% in the examples are based on weight.

Example 1 200 parts of a pulverized waste compact disc and 300 parts of a 3% aqueous sodium hydroxide solution were charged into a flask and stirred at 70 ° C. for 20 minutes. Then, the mixture was cooled and neutralized with dilute hydrochloric acid, and the extracted mixture was washed with running water,
The peeled processing layer (aluminum, protective layer, printed layer, etc.) was removed and dried to recover 193.0 parts of the polycarbonate resin.

(A) Polycarbonate resin 9 obtained
6.6 parts of phenol (water content 0.01%) 701.
Two parts were added and the mixture was refluxed for 1 hour under normal pressure. When the obtained reaction mixture was analyzed by a high performance liquid chromatograph, it contained bisphenol A: 10.65% and diphenyl carbonate: 5.98%.

(B) A packed column type distillation column (using a Sulzer packing EX) having an inner diameter of 20 mm and a height of 1 m.
The distillation column overhead temperature was maintained at 150 ° C. and 300 Torr to distill off phenol, and then the overhead temperature was adjusted to 20
The temperature was raised to 0 ° C. and maintained at 50 Torr to distill diphenyl carbonate. Diphenyl carbonate 79.
7 parts were collected. The purity was 99.5%.

(C) Next, 200 parts of phenol was added to the solution obtained from the bottom of (B) and heated at 150 ° C. under normal pressure for 20 minutes while stirring, and then at a rate of 1 ° C./minute. Cooled slowly to 45 ° C. The crystals were separated by filtration and washed twice with 100 parts of phenol.

(D) Next, the crystals were heated and melted, and phenol was distilled off while continuously feeding the crystals to a small glass thin film evaporator, and bisphenol A was taken out from the bottom of the column. 69.9 parts of bisphenol A was obtained, and the purity was 99.8%.

[Brief description of drawings]

FIG. 1 shows an example of the process of the present invention.

[Explanation of symbols]

1: First step of the present invention (waste polycarbonate resin (waste PC) is heated with phenols to carry out transesterification reaction) 2: Second step of the present invention (containing phenols from transesterification reaction product) Diphenyl carbonate is separated by distillation.) 3-1: Third step of the present invention (after adding phenols and heating to form an adduct of BPA and phenols,
Cool to crystallize the adduct. ) 3-2: Third step of the present invention (separate adduct) 4: Fourth step of the present invention (recover bisphenol A by removing phenols of adduct) 5: Phenols and diphenyl Step of separating carbonate (phenols are recycled by adding a shortage) 6: Step of recovering (for example, evaporating) phenols from the mother liquor after separation of the adduct.

Claims (1)

[Claims] 1. When recovering an aromatic dihydroxy compound and a diaryl carbonate compound by a transesterification reaction between a waste aromatic polycarbonate resin and an aromatic monohydroxy compound, (A) the aromatic polycarbonate resin and the aromatic monohydroxy compound are combined with each other. It remains in the first step of transesterification, the second step of distilling and separating the diaryl carbonate compound containing the aromatic monohydroxy compound from the reaction product obtained in the first step of (B), and the second step of (C). Aromatic monohydroxy compound is added to aromatic dihydroxy compound and heated to form an adduct of both, and then the adduct is crystallized by cooling to obtain a third step and (D) third step. After melting the obtained crystals by heating, the aromatic monohydroxy compound is distilled off to form an aromatic dihydroxy compound. A method for recycling a waste aromatic polycarbonate resin, comprising the fourth step of obtaining a product.