JPH0747665B2 - 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, the recovered phenolic compound is easily colored, and the polycarbonate obtained by using the compound is also colored. Further, according to this method, the solubility of the phenolic compound in acidic water cannot be recovered during the acid precipitation, and the saturation solubility in water cannot be recovered during the purification.

<Purpose of the Invention> The present invention efficiently recovers unreacted phenolic compounds in reaction waste water in the production of polycarbonate with high purity and uses them in the production reaction of polycarbonate to improve production yield and to obtain high quality. The purpose is to provide a polycarbonate.

The present inventors have found that even if the reaction waste water is alkaline, the phenolic compound can be efficiently extracted by bringing it into contact with an organic solvent. 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. As a result of further studies conducted by the present inventor based on this finding, the organic solvent solution in which the phenolic compound was extracted was observed to be colored, and if the organic solvent solution was used as it was, the color tone of the obtained polycarbonate deteriorated. If a caustic aqueous solution is further contacted with this organic solvent solution, a highly pure phenolic compound excluding the coloring components can be recovered.If a caustic aqueous solution containing this phenolic compound is used, the color tone The inventors have completed the present invention knowing that a good polycarbonate can be obtained.

<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 phenolic compound is extracted by bringing 5% by volume or more of an organic solvent into contact with the reaction wastewater, and then a caustic aqueous solution is brought into contact with the organic solvent solution from which the phenolic compound has been extracted to obtain a phenolic compound. The method for producing a polycarbonate is characterized in that the aqueous solution of caustic alkali is transferred to the aqueous solution of caustic alkali, and the obtained aqueous solution of caustic alkali is used in the above reaction.

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 phenolic compound salt generated during the production of a polycarbonate by reacting an aqueous solution of the above-mentioned phenolic compound (usually caustic soda) with phosgene is 10 or less. , Preferably 5 to 10, particularly preferably 6 to 9. This PH 10
When it is higher, it becomes difficult to sufficiently extract the phenolic compound. Organic acids and mineral acids are used to adjust pH,
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.

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.

The organic solvent solution containing the phenolic compound thus extracted is allowed to stand to separate it from the aqueous layer, and the separated organic solvent solution is further contacted with a caustic alkaline aqueous solution to causticize the phenolic compound in the organic solvent solution. Transfer to an alkaline aqueous solution.

The caustic alkali used here is preferably sodium hydroxide or potassium hydroxide. The concentration of the caustic aqueous solution is preferably in the range of 3 to 15% by weight, particularly preferably 5 to 10% by weight. The amount of the caustic aqueous solution used is preferably 1/4 to 5 times the volume of the organic solvent solution to be contacted, and particularly preferably 1/2 to 3 times the volume.

In order to bring the organic solvent solution into contact with the aqueous caustic solution to transfer the phenolic compound in the organic solvent solution into the aqueous caustic solution, as in the case of contacting the reaction wastewater with the organic solvent, both may be stirred and mixed. .

Thus, when the caustic aqueous solution containing the phenolic compound is used in the production reaction of the polycarbonate, it is preferable to correct the new raw material by that amount, but the amount of the phenolic compound in the caustic aqueous solution is new. If the amount is 0.01% by weight or less based on the charged phenolic compound, neither reaction yield nor quality is affected without 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 and highly recovered from the reaction wastewater generated during the production of polycarbonate, and can be effectively reused, so that a high-quality polycarbonate can be obtained. It can be produced in high yield, and its industrial effect is exceptional.

<Examples> The present invention will be described in detail with reference to Examples. The concentration of the phenolic compound and the color tone b value 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
Was calculated by substituting 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) Color tone b value 50 × 50 × with injection molding machine A 2 mm sample plate was molded and measured with a color difference meter (manufactured by Suga Test Instruments Co., Ltd.).

Example 1 433.3 g of 25% by weight aqueous sodium hydroxide solution was placed in a two-neck flask equipped with a phosgene suction tube, a thermometer and a stirrer.
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 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 a methylene chloride layer and a 1150 ml aqueous layer (reaction waste water).

The separated methylene chloride solution was washed with water to remove methylene chloride to obtain a polycarbonate powder. The powder had a viscosity average molecular weight of 23,500 after being dried at 140 ° C. for 6 hours with a hot air circulation dryer. The b value of the sample board was 4.2. On the other hand, the concentration of residual phenolic compounds in the separated reaction wastewater was 3.00 g /, and the total amount of phenolic compounds contained in the reaction wastewater was 3.45 g.

The total amount (1150 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 8 with a 35.5 wt% hydrochloric acid aqueous solution with stirring, and the mixture was stirred for 10 minutes and then allowed to stand still. The mixture was placed and separated into a methylene chloride layer and an aqueous layer. The concentration of residual phenolic compounds in the aqueous layer is 0.
It was 04 g / and was discarded. Total amount of methylene chloride solution (600 ml) separated and 25 wt% sodium hydroxide aqueous solution 43
3.3 g of water, 850 ml of water and 0.5 g of hydrosulfite were placed in a separable flask No. 2 equipped with a stirrer, stirred for 10 minutes and then left to stand to separate into a methylene chloride layer and a 1188 ml water layer (caustic alkaline aqueous solution). The concentration of residual phenolic compounds in the separated caustic aqueous solution was 2.84 g /, the total amount of phenolic compounds contained in the caustic aqueous solution was 3.37 g, and the recovery rate was 97.7%.

The total amount of this caustic aqueous solution (1188 ml) was used in place of 43% by weight of a 25% by weight aqueous sodium hydroxide solution, 850 ml of water and 0.5 g of hydrosulfite.
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 reaction wastewater was 3.06 g /. The b value of the sample board was 4.3.

Example 2 433.3 g of 25% by weight aqueous sodium hydroxide solution was placed in a two-necked flask equipped with a phosgene blow-in tube, a thermometer and a stirrer.
850 ml of water, 0.5 g of hydrosulfite and 239.0 g of bisphenol A were added and dissolved with stirring. After dissolution, 600 ml of methylene chloride was added, and 118.1 g of phosgene was blown in for 100 minutes to carry out the reaction while maintaining the liquid temperature within the range of 22 ± 2 ° C. under stirring.
After completion of the blowing, 10.0 g of pt-butylphenol and 0.36 ml of triethylamine were added, and the mixture was stirred at 32 ± 2 ° C. for 1 hour to complete the polymerization. Thereafter, in the same manner as in Example 1, a 1165 ml aqueous layer (reaction waste water) and a polycarbonate were obtained. The viscosity average molecular weight of the polymer was 16,000, and the b value of the sample plate was 4.0. On the other hand, the concentration of residual phenolic compounds in the reaction wastewater was 2.00 g /, and the total amount of phenolic compounds contained in the reaction wastewater was 2.33 g.

The total amount of this reaction wastewater (1165 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 allowed to stand, and a methylene chloride layer and an aqueous layer were separated. The concentration of residual phenolic compound in the aqueous layer was 0.04 g / and was discarded. The total amount (600 ml) of the separated methylene chloride solution, 433.3 g of a 25 wt% sodium hydroxide aqueous solution, 850 ml of water and 0.5 g of hydrosulfite were placed in a 2 separable flask equipped with a stirrer, stirred for 10 minutes and then allowed to stand. Then, it was separated into a methylene chloride layer and a 1188 ml aqueous layer (caustic alkaline aqueous solution). The concentration of residual phenolic compounds in the separated aqueous caustic solution was 1.90 g /
The total amount of phenolic compounds contained in the aqueous caustic solution was 2.26 g, and the recovery rate was 97.0%.

The total amount of this caustic aqueous solution (1188 ml) was used in place of 43% by weight of a 25% by weight aqueous sodium hydroxide solution, 850 ml of water and 0.5 g of hydrosulfite.
Except that the amount used was changed to 236.7 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 16,000, and the concentration of the residual phenol compound in the reaction wastewater was 2.00 g /. The b value of the sample board was 3.9.

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. PH
A phenolic compound is extracted by bringing the reaction wastewater into contact with 5% by volume or more of an organic solvent with respect to the reaction wastewater, and then an organic solvent solution from which the phenolic compound is extracted is brought into contact with a caustic aqueous solution to obtain a phenolic compound. Is transferred to the caustic aqueous solution, and the resulting caustic aqueous solution is used for the above reaction.