JPH0747666B2 - Polycarbonate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention: The present invention efficiently recovers a phenolic compound from a reaction wastewater containing a salt of an unreacted phenolic compound generated in a reaction during the production of a polycarbonate. The present invention relates to a method of improving the production yield by reusing it in a production reaction.

<Prior art and its problems> As a method for producing a polycarbonate, a so-called solution method in which an alkaline aqueous solution of a phenolic compound and phosgene are reacted in the presence of an organic solvent is widely adopted. This method generates a considerable amount of reaction wastewater, and in this reaction wastewater there are unreacted divalent phenolic compounds used as raw materials and monovalent phenolic compounds used as terminal terminators. .

Conventionally, as a method of recovering a phenolic compound from reaction wastewater in the production of polycarbonate, a method of separating a phenolic compound precipitated by acid folding by filtration is known.

However, since the phenolic compound recovered by this method has many impurities and is in a solid state, complicated steps such as purification, drying and weighing are required for reuse. Moreover, in order to improve the recovery rate of the phenolic compound, PH is 5 or less,
Since it is preferably 3 or less, corrosion of the equipment used is likely to occur. Further, in this method, the solubility of the phenolic compound in acidic water cannot be recovered during acid precipitation,
It cannot be recovered from wastewater containing low concentrations of phenolic compounds that do not reach saturated solubility in water.

<Object of the Invention> An object of the present invention is to efficiently recover the unreacted phenolic compound in the reaction waste water in the production of polycarbonate and reuse it in the production reaction of polycarbonate to improve the production yield.

The present inventor has made it possible to efficiently extract phenolic compounds by bringing the pH of the above-mentioned reaction wastewater into an appropriate alkaline to bring it into contact with an organic solvent, and to reuse the obtained organic solvent solution as it is for the production of polycarbonate. I found it. Generally, a phenolic compound becomes a salt in an alkaline aqueous solution and becomes water-soluble. Therefore, it is usually considered that the contact with an organic solvent predominantly distributes it to an aqueous system. However, it is surprising that the organic solvent can be efficiently extracted. Moreover, since it is performed in an alkaline manner, there is no corrosion of the equipment and it is extremely effective. The present invention has been completed as a result of further intensive studies based on this finding.

<Structure of the Invention> The present invention relates to a method for producing a polycarbonate by reacting an alkaline aqueous solution of a phenolic compound with phosgene in the presence of an organic solvent, which contains an unreacted phenolic compound salt generated from the reaction. PH of reaction wastewater
A polycarbonate characterized in that the phenolic compound is extracted by contacting an organic solvent of 5% by volume or more with the reaction waste water to a higher value and 10 or less, and using the obtained organic solvent solution in the above reaction. It is a manufacturing method.

The phenolic compound referred to in the present invention is a divalent phenolic compound used as a raw material in the production of a polycarbonate or a monovalent phenolic compound used as a terminal terminating agent, and is a compound in which a hydroxyl group is directly bonded to an aromatic nucleus. For example, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 1,1-bis (4-hydroxyphenyl) ethane, bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxy) (Phenyl) cyclohexane, phenol, pt-butylphenol, octylphenol, nonylphenol and the like.

Examples of the organic solvent used in the present invention include methylene chloride, 1,2-dichloroethane, tetrachloroethane, chlorinated aliphatic hydrocarbons such as chloroform, aromatic hydrocarbons such as benzene, toluene and xylene, and chlorine-substituted products thereof. Among them, methylene chloride is preferable. Moreover, these can be used individually or in mixture of 2 or more types.

In the present invention, the pH of the reaction waste water containing the unreacted salt of a phenolic compound generated when a polycarbonate is produced by reacting an aqueous solution of the above-mentioned phenolic compound (usually sodium hydroxide) with phosgene. Is in the range of more than 5 and 10 or less, preferably 6-9. If this PH is set to 5 or less, the equipment used will be corroded, and if it is higher than 10, it will be difficult to sufficiently extract the phenolic compound. Organic acids and mineral acids are used to adjust the pH, but hydrochloric acid or sulfuric acid is preferred.

The phenolic compound in the reaction wastewater is extracted by bringing the organic solvent into contact with the reaction wastewater adjusted to the pH. Specifically, a predetermined amount of organic solvent is added to the reaction wastewater in advance and then adjusted to a predetermined PH, or a predetermined amount of organic solvent is added to the reaction wastewater adjusted to a predetermined PH and mixed and stirred. Good. It should be noted that even if a catalyst such as triethylamine is dissolved in the reaction wastewater, there is no problem.

Any means may be adopted for stirring, but it is particularly preferable to perform high-speed stirring with a homogenizer, a mixer, a homomic line flow, etc., and an orifice mixer, a static mixer, a colloid mill, a flow jet mixer, an ultrasonic emulsifier, etc. Is also preferably used. When using a simple stirrer, it is preferable to stir for 5 minutes or more, particularly 10 minutes or more. Since the equipment used has a high PH, it is not necessary to perform corrosion resistance treatment such as lining.

The amount of the organic solvent used must be 5% by volume or more with respect to the amount of reaction wastewater. If the amount does not reach 5% by volume, it is difficult to sufficiently extract the phenolic compound.

In this way, when using the organic solvent solution containing the unreacted phenolic compound for the production reaction of the polycarbonate, it is preferable to correct the new charging material by that amount, but the amount of the phenolic compound in the organic solvent is If 0.01% by weight or less based on the new charged phenolic compound,
There is no effect on the reaction yield or quality without any particular correction.

The method of the present invention can be applied to both a batch method and a continuous method by the non-catalytic method and the catalytic method.

In the present invention, the aqueous layer (reaction wastewater) separated from the organic solvent layer containing the polycarbonate is used by standing or centrifuging after completion of the production reaction of the polycarbonate. Reducing antioxidants such as hydrosulfite may be present during the entire reaction and extraction process to prevent coloration of the resulting phenolic compounds, and this is also preferred.

<Effects of the Invention> According to the method of the present invention, unreacted phenolic compounds can be efficiently recovered in the neutral to alkaline range from the reaction wastewater generated during the production of a polycarbonate resin, and can be effectively reused. The yield can be improved, and there are particular effects such as no corrosion of equipment.

<Examples> The present invention will be described in detail with reference to Examples. The concentration of the phenolic compound and the recovery rate of the phenolic compound were determined by the following methods.

(I) Concentration of Phenolic Compound A fixed amount of wastewater containing a phenolic compound was placed in a volumetric flask and diluted with sodium hydroxide and water 100 times to have a pH of 13 to 14 at 294.0 nm. UV absorption spectrometer (Hitachi U320
It was determined by substituting it in the following formula.

A = 100 ・ W / (22.02 ・ l) A: Phenolic compound concentration (g /) W: Absorbance at 294.0nm l: Cell optical path length (cm) (ii) Recovery rate of phenolic compound by organic solvent = {(AB) / A} × 100 A: Phenolic compound concentration in reaction wastewater (g /) B: Phenolic compound concentration in wastewater after extraction (g /) Example 1 Phosgene suction pipe, In a two-necked flask equipped with a thermometer and a stirrer, 433.3 g of 25% by weight aqueous sodium hydroxide solution,
Water 850ml, Hydrosulfite 0.5g, Bisphenol A
239.0 g and 600 ml of methylene chloride were added and dissolved by stirring. After dissolution, 118.0 g of phosgene was blown in for 60 minutes to carry out the reaction while maintaining the liquid temperature under stirring within the range of 22 ± 2 ° C. After the completion of blowing, 4.27 g of pt-butylphenol was added, and the liquid temperature was set to 32 ±.
Polymerization was completed by maintaining the temperature in the range of 2 ° C. and stirring for 150 minutes. After the completion of the polymerization, 600 ml of methylene chloride was added, and the mixture was stirred for 5 minutes and allowed to stand to separate the methylene chloride layer and the 1153 ml aqueous layer (reaction waste water).

The separated methylene chloride solution was washed with water to remove methylene chloride to obtain a polycarbonate powder having a viscosity average molecular weight of 23,500. On the other hand, the concentration of the residual phenolic compound in the separated reaction waste water was 3.00 g /.

The total amount (1153 ml) of this reaction waste water and 600 ml of methylene chloride were put into a separable flask of 2 equipped with a reflux condenser and a stirrer, the pH was lowered to 7.1 with a 35.5 wt% hydrochloric acid aqueous solution with stirring, and the mixture was stirred for 10 minutes and then allowed to stand. The mixture was placed and separated into a methylene chloride layer and an aqueous layer. The concentration of residual phenolic compounds in the water layer is
At 0.05 g /, the recovery rate of phenolic compounds (methylene chloride extraction rate) was 98.3%, and the total amount of phenolic compounds contained in the methylene chloride solution was 3.40 g. No corrosion of the container was observed.

The total amount of the separated methylene chloride solution (600 ml) was used in place of 600 ml of new methylene chloride, and bisphenol A was added.
Except that the amount used was changed to 235.6 g to carry out the reaction under the same conditions as above to obtain a polycarbonate and an aqueous layer (reaction waste water). The viscosity average molecular weight of the polymer was 23.400, and the concentration of the residual phenol compound in the aqueous layer was 3.02 g /.

Example 2 500 ml of reaction waste water (residual phenolic compound concentration: 2.1 g /) obtained by reacting under the same conditions as in Example 1 and 150 ml of methylene chloride were placed in a separable flask 1 equipped with a reflux condenser and a stirrer. , PH with 2.2%, 6.8, 7.8, 9.0, 10.1, 10.7, 11.2 in 35.5 wt% hydrochloric acid aqueous solution under stirring
Methylene chloride extraction was carried out in the same manner as in Example 1 for the case of pH 13.3 and the case of PH 13.3 in which the hydrochloric acid aqueous solution was not used. The concentration of the phenolic compound in the aqueous layer at each PH was measured, and the recovery rate of the phenolic compound (methylene chloride extraction rate) was determined and shown in FIG. As is clear from the figure
When the pH exceeds 10, the recovery rate of the phenolic compound deteriorates sharply. Moreover, the corrosion of the container was not observed at PH6.8 or higher, but the corrosion of the container surface was remarkable at PH2.25.

Example 3 In a two-necked flask equipped with a phosgene blow-in tube, a thermometer and a stirrer, 315.0 g of a 25 wt% sodium hydroxide aqueous solution,
780 ml of water, 0.5 g of hydrosulfite and 236.7 g of bisphenol A were added and dissolved by stirring. After dissolution, 600 ml of methylene chloride and 37.0 g of 48% by weight sodium hydroxide aqueous solution were added, and 118.1 g of phosgene was blown in for 100 minutes to carry out the reaction while keeping the liquid temperature within the range of 22 ± 2 ° C. under stirring. After the completion of blowing, 10.0 g of pt-butylphenol, 24.0 g of 48% by weight sodium hydroxide, 2.3 g of bisphenol A and 0.9 g of sodium hydroxide dissolved in 23.0 ml of water, and 0.36 ml of triethylamine were added at 32 ± 2 ° C. Polymerization was completed by stirring for 1 hour. Thereafter, in the same manner as in Example 1, an aqueous layer (reaction wastewater) 1160
Obtained ml and polycarbonate. The viscosity average molecular weight of the polymer was 16,000, and the concentration of the residual phenolic compound in this aqueous layer was 2.00 g /.

The total amount of this reaction wastewater (1160 ml) and methylene chloride 600 ml
Was placed in a separable flask (2) equipped with a reflux condenser and a stirrer, and PH was adjusted to 6 with a 35.5 wt% hydrochloric acid aqueous solution with stirring.
The mixture was lowered to 0, stirred for 10 minutes and then left to stand to separate into a methylene chloride layer and an aqueous layer. The concentration of residual phenolic compound in the aqueous layer was 0.04 g /, the recovery rate of phenolic compound (methylene chloride extraction rate) was 98.0%, and the phenolic compound contained in the methylene chloride solution was 2.27 g. It was

The total volume of this methylene chloride solution (600 ml) was used instead of 600 ml of new methylene chloride, and the polycarbonate and water layer (reaction wastewater) were reacted in the same manner as above except that the amount of bisphenol A used was changed to 234.4 g. Got

The viscosity average molecular weight of the polymer was 15,900, and the concentration of the residual phenolic compound in the reaction wastewater was 1.96 g /, and even if the recovered phenolic compound was used, the reaction was not adversely affected.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the pH of reaction waste water and the extraction rate with methylene chloride.

Claims (1)

[Claims] 1. A method for producing a polycarbonate by reacting an alkaline aqueous solution of a phenolic compound with phosgene in the presence of an organic solvent, which comprises reacting waste water containing a salt of an unreacted phenolic compound generated from the reaction. The pH is higher than 5 and 10 or less, and 5 for the reaction wastewater.
A method for producing a polycarbonate, wherein a phenolic compound is extracted by contacting with an organic solvent in a volume% or more, and the obtained organic solvent solution is used in the above reaction.