JPH0959372A - Production of polycarbonate resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polycarbonate resin retaining its heat resistance and hue, by interfacial polymerization with reduced use of a mineral acid for neutralizing the resultant resin solution. SOLUTION: (A) An aromatic bisphenol compound is dissolved in (B) an aqueous caustic alkali solution followed by conducting a phosgenation reaction to carry out a polymerization. Subsequently, a mineral acid (pref. phosphoric acid and/or phosphorous acid) is added to the resultant polycarbonate resin solution containing the caustic alkali to neutralize the resin solution followed by separating the resin solution and the aqueous layer, and 20-80vol.% of the aqueous layer is recovered and used for the neutralization again. It is preferable to add the mineral acid so that the pH of the aqueous layer after the neutralization is <=4. The component A is e.g. 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4- hydroxyphenyl)cyclohexane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarbonate resin, and more specifically, in obtaining a polycarbonate resin by an interfacial polymerization reaction, the amount of mineral acid used for neutralizing a polycarbonate resin solution is reduced, The present invention also relates to a method that does not reduce the heat resistance and hue of the obtained polycarbonate resin during molding.

[0002]

2. Description of the Related Art Polycarbonate resin production methods are roughly classified into a solution polymerization method and a melting method (transesterification method). Solution polymerization methods include pyridine method and interfacial polymerization method.
Conventionally, an interfacial polymerization method has been the mainstream for the production method of a polycarbonate resin.

In the interfacial polymerization method, aromatic bisphenol is dissolved in a caustic solution, reacted with phosgene in the presence of an organic solvent, and if necessary, a polycondensation catalyst is added and stirred to complete the polymerization reaction. Polycarbonate resin obtained by this polymerization method is obtained as a resin solution dissolved in an organic solvent, but since the polymerization reaction proceeds in an alkaline atmosphere, other by-products such as chloride and carbonate are included in the resin solution. , Caustic remains. If an alkaline substance such as caustic alkali remains in the polycarbonate, it adversely affects the heat resistance and the hue. Therefore, it is usually necessary to add a mineral acid to the polycarbonate resin solution to neutralize the caustic alkali.

[0004]

Phosphoric acid, hydrochloric acid, sulfuric acid, etc. are used as the mineral acid, but the theoretical amount of mineral acid is added in excess for the purpose of completely neutralizing the caustic. That is usually done. After neutralizing with mineral acid, the resin solution is separated by operations such as centrifugation.
The water layer containing excess mineral acid is removed and drained. However, since the aqueous layer containing unreacted mineral acid is highly acidic,
Since it is an environmental problem to drain the water from the system as it is,
Wastewater treatment equipment for adjusting the pH value of the wastewater is required.

Furthermore, in recent years, the management of the phosphorus concentration in wastewater has been severely restricted due to measures against eutrophication in lakes and inland seas. Especially,
In a polycarbonate resin manufacturing plant, when using a mineral acid containing phosphorus atoms such as phosphoric acid or phosphorous acid as a mineral acid for neutralization, it is necessary to minimize the amount of the mineral acid used. Become.

Therefore, the present inventors have paid attention to the fact that unreacted mineral acid remains in the acid wastewater of the aqueous layer separated after the neutralization reaction, and as a result of diligent study, I arrived.

[0007]

Means for Solving the Problems That is, the present invention relates to an interfacial polymerization reaction of a polycarbonate resin in which an aromatic bisphenol compound is dissolved in a caustic aqueous solution, and a phosgenation reaction is carried out in the presence of an organic solvent to carry out a polymerization reaction. To the polycarbonate resin solution containing caustic alkali obtained by the polymerization reaction, mineral acid is added to neutralize the resin solution, and then the resin solution and the aqueous layer are separated, and 20 to 80% (volume) of the separated aqueous layer Is recovered and used again in the neutralization reaction. Preferably, the mineral acid used for neutralization is phosphoric acid and / or phosphoric acid, and further, the mineral acid is added so that the pH value of the neutralized aqueous layer is 4 or less. Is the method. Since the amount of mineral acid used can be reduced by the method of the present invention, the load on wastewater treatment equipment can be reduced. It was also found that the polycarbonate resin obtained by the method of the present invention is comparable in heat resistance and hue to the polycarbonate resin of the conventional method.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below.
The polycarbonate resin referred to in the present invention is produced by a conventional method for producing a polycarbonate resin, that is, a solution method such as an interfacial polymerization method or a pyridine method, which contains a dihydric phenol compound as a main component and a small amount of a molecular weight modifier or It is prepared by reacting with phosgene using a terminal stopper and optionally a branching agent. Aromatic homo or copolycarbonate resins using bisphenols, further branched ones, ones having a long-chain alkyl group introduced at the end thereof, those having a viscosity average molecular weight of 13,000 to 100,000. Applicable. Further, as a terminal terminating agent or a comonomer, a polycarbonate resin having a double bond obtained by reacting a compound having a carbon-carbon double bond is produced, and a polycarbonate resin having a styrene or the like graft-reacted thereto, or a phenol to polystyrene or the like. Any of a hydroxyl group and a polycarbonate resin obtained by graft-polymerizing another reactive monomer can be applied. Among these, as the aromatic polycarbonate resin, there is particularly mentioned a polycarbonate containing bisphenol A as a main raw material, and examples thereof include bisphenol Z and tetrabromobisphenol A.
A polycarbonate copolymer obtained by using (TBA) or the like in combination, a branched product thereof, or a product modified with an alkyl having a long-chain terminal is preferable.

The preferred bisphenol compounds used in the method for producing the polycarbonate resin of the present invention are specifically bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) ether and bis (4-hydroxyphenyl). ) Sulfone, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) ketone, 1,1-bis (4-hydroxyphenyl)
Ethane, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A; BPA), 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane 2 (TBA), 2-bis ( 4-hydroxyphenyl)
Butane, 1,1-bis (4-hydroxyphenyl) cyclohexane (bisphenol Z; BPZ), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4- Hydroxy-3,5-dichlorophenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4-
(Hydroxy-3-chlorophenyl) propane, 2,2-
Bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) diphenylmethane, α, ω-bis [3- (O
Examples include -hydroxyphenyl) propyl] polydimethylsiloxane (PDS) and biphenol. You may use these in combination of 2 or more types. Among them, those selected from bisphenol A, bisphenol Z, TBA and PDS are preferable.

In the present invention, a terminal stopper or a molecular weight modifier can be used. Examples of the terminal terminator or the molecular weight modifier include compounds having a monovalent phenolic hydroxyl group. In addition to ordinary phenol, pt-butylphenol, tribromophenol, etc., long chain alkylphenols, aliphatic carboxylic acid chlorides, Examples thereof include aliphatic carboxylic acid, aromatic carboxylic acid, aromatic acid chloride, hydroxybenzoic acid alkyl ester, and alkyl ether phenol. Further, it may be used as a terminal terminating agent having a reactive double bond, and examples thereof include acrylic acid, vinyl acetic acid, 2-pentenoic acid, 3-pentenoic acid, 5-hexenoic acid, 9-undecenoic acid and the like. Acid chlorides or chloroformates such as rucohol chloroformate, isopropenylphenol chloroformate or hydroxystyrene chloroformate; isopropenylphenol, hydroxystyrene,
Examples thereof include phenols having an unsaturated group such as hydroxyphenylmaleimide, hydroxybenzoic acid allyl ester, and hydroxybenzoic acid methylallyl ester. Of these, phenol and pt-butylphenol are preferable.

The amount of the terminal terminator or the molecular weight modifier used is usually 1 to 25 mol%, preferably 1.5 to 10 mol based on 1 mol of the above dihydric phenol compound.
It is used in the range of mol%. Further, the terminal stopper can be added in the state of an organic solvent solution or an aqueous solution of caustic, but if left in the state of an alkaline aqueous solution,
Since it discolors red and affects the hue of the molded product of the polycarbonate resin, it is preferably added as an organic solvent solution, usually 10 to 30% by weight.

In the present invention, examples of the organic solvent used include chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane and carbon tetrachloride; aromatic carbonization such as benzene. Hydrogen; ether compounds such as diethyl ether may be mentioned, and two or more kinds of these organic solvents may be mixed and used. In addition, if desired, solvents other than the above, such as ethers, ketones, esters, and nitriles, which have an affinity for water may be used within the limit that the mixed solvent system is not completely compatible with water.

Further, the branching agent is used in an amount of 0.01 to 3 mol%, particularly 0.1 to 3 mol% based on the above dihydric phenol compound.
A branched polycarbonate can be obtained by using together in the range of 1.0 mol%. As a branching agent, phloroglucin, 2,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptene-3,4,6-dimethyl-
2,4,6-tri (4-hydroxyphenyl) heptene-2,1,3,5-tri (2-hydroxyphenyl) benzole, 1,1,1-tri (4-hydroxyphenyl) ethane, 2,6 -Bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, α, α ', α "
-Polyhydroxy compounds exemplified by tri (4-hydroxyphenyl) -1,3,5-triisopropylbenzene and 3,3-bis (4-hydroxyphenyl)
Oxindole (= isatin bisphenol), 5-
Examples include chloroisatin bisphenol, 5,7-dichloroisatin bisphenol, and 5-bromoisatin bisphenol.

Usually, in the interfacial polymerization reaction, an aromatic bisphenol compound is dissolved in a caustic aqueous solution, a phosgenation reaction is carried out in the presence of an organic solvent, a polycondensation catalyst is added if necessary, and the polymerization reaction is carried out by stirring. I do. After the completion of the polymerization reaction, the resin solution of the polycarbonate of the organic layer and the aqueous layer containing by-products such as chloride, carbonate and caustic are separated. When the separation is insufficient, it is separated by a means such as static separation or centrifugation.

Usually, the polycarbonate resin solution after the polymerization reaction is obtained at a concentration of 4 to 27 w / w%, but in order to efficiently carry out the neutralization reaction using a mineral acid, it is previously set to 19 w / w% or less. It is preferable to dilute to Since the resin solution contains unreacted bisphenol monomer in addition to water containing a salt as a by-product, caustic alkali is added to the resin solution and stirred before neutralization with a mineral acid. It is preferable to extract the reacted bisphenol monomer to the water layer side and centrifuge to remove the water layer.

A mineral acid is added to a polycarbonate resin solution containing a caustic aqueous solution to carry out a neutralization reaction. Since the resin solution contains alkaline fine water droplets, it is preferable to stir by giving a strong shearing force so that each fine water droplet is neutralized. As the concentration of mineral acid,
For efficient dispersibility in a resin solution, it is preferable to dilute with water and add it as a concentration of 0.1 to 30 w / v%, and more preferably to a concentration range of 0.1 to 10 w / v%. Is.

The amount of the mineral acid used varies depending on the concentration of the mineral acid, and in order to completely neutralize the caustic alkali in the resin solution, a slight excess of the theoretical value is added to the neutralized water layer. It is preferable to add it so that the pH value is 4 or less,
More preferably, the amount of mineral acid added is determined so as to fall within the range of 0.5 to 3.5.

The mixed solution of the polycarbonate resin solution and the mineral acid is subjected to static separation, preferably centrifugation, to separate the polycarbonate resin solution and the aqueous layer. In the water layer, unreacted free mineral acid is dissolved in addition to the salt produced by the neutralization reaction of mineral acid and caustic. In the present invention, the water layer is recovered and used again for the neutralization reaction, but if the amount of the water layer to be recovered is too high, the impurities are concentrated in the recovered water and the impurities remain in the resin solution. It is not preferable. 20 ~ of the water layer separated by centrifugation etc.
It is preferable to make the amount equivalent to 80% (volume). The amount of the aqueous layer to be recovered is usually in the range of 30 to 80% for the purpose of increasing the recovery rate and suppressing the amount of the mineral acid used as much as possible.

The recovered aqueous layer can be reused as it is for the neutralization reaction, but it should be reused by newly replenishing with mineral acid corresponding to the amount consumed in the neutralization reaction. Is preferred. The amount of mineral acid to be replenished is preferably added so that the pH value of the aqueous layer after the neutralization reaction is 4 or less.

The polycarbonate resin solution obtained by the above method is washed by adding pure water as necessary and stirring and mixing, and then centrifuged to obtain a purified polycarbonate resin solution. The purified resin solution can be granulated by a conventional method such as dropping it into warm water under stirring or adding it to a kneader or the like. Polycarbonate resin granules containing solvent and water,
By drying with a dryer, a granular material suitable for extrusion processing and molding processing can be obtained.

[0021]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist.

(1) Preparation of polycarbonate resin solution;
In an agitator tank with an internal volume of 100 L equipped with an agitator agitator (manufactured by Shimazaki Seisakusho Co., Ltd., triangular type two blades, reversal number 135 cpm), 7 kg of bisphenol A, 31 L of 8.8 w / w% sodium hydroxide aqueous solution, hydrosulfite (H
D) 30 g was added to dissolve bisphenol A, 11 L of methylene chloride was added, and 3.4 kg of phosgene was blown in for 30 minutes while stirring with an agitator-type stirrer to perform a phosgenation reaction. After completion of the phosgenation reaction, stirring was stopped, and the mixture was allowed to stand for 5 minutes for separation, and then 2.8 g of p-t-butylphenol dissolved in 2 L of methylene chloride was used as a terminal stopper in the reaction solution, and 8.8% sodium hydroxide. Aqueous solution 4L and methylene chloride 9L were added and stirred. After 5 minutes, 50 mL of triethylamine was added as a polymerization catalyst to the reaction solution under stirring, and the mixture was further added to 60 mL.
The mixture was stirred for a minute to complete the polymerization reaction. The polymer resin solution was separated into an alkaline water layer and two layers of a polycarbonate resin solution. The upper liquid was removed, 5 L of methylene chloride and 10 L of pure water were added to the resin solution, and the mixture was stirred with an agitator, and the mixture was separated into a polycarbonate resin solution containing caustic by a centrifuge. When the concentration was obtained by concentrating this resin solution by heating, it was 19 w / w%.

(2) Preparation of water layer after acid neutralization: To 70 L of the obtained caustic-containing polycarbonate resin solution, 10 L of 1.0 w / w% phosphoric acid was added, and a homomixer (special machine) was used. The mixture was stirred for 30 minutes using a chemical method and then centrifuged to separate an acidic polycarbonate resin solution and an acidic waste water. The amount of waste water was 9.98 L, and the pH value was measured and found to be 1.7.

(3) Extrusion of dry powder: The powder dried by the dryer was fed to a twin-screw vent extruder (screw diameter 65 mm, total length L / D = 30, vent part Lv / D = 4). The solvent was distilled off during extrusion and pelletized. The extrusion conditions were a maximum resin temperature of 280 ° C. and a vent pressure of 9 Torr.

(4) Hue evaluation method: Each pellet was held by an injection molding machine (neomat 350/120 manufactured by Sumitomo Heavy Industries, Ltd.) at a resin temperature of 320 ° C. and a mold temperature of 80 ° C. 50 mm x 60 at a pressure of 1000 kg / cm ²
Five plate pieces having a thickness of 3 mm and a thickness of 3 mm were continuously molded, and the molded pieces were color-measured by a color difference meter manufactured by Nippon Denshoku Co., Ltd. to obtain a YI value (an index indicating yellowness).

(5) Melting test: 4 g of pellets were put in a test tube, dried at 120 ° C. for 4 hours in a dryer, and then the test tube was placed in a 34
Insert into a block bath maintained at 0 ° C, and under a nitrogen stream,
After melting for a period of time, the viscosity average molecular weight before and after melting was determined by GPC measurement, and the decrease in molecular weight was investigated.

Example 1 To 70 L of an alkaline polycarbonate resin solution obtained by the same method as in (1) above, 3 L of acid wastewater (30% recovery) obtained in (2) above and 1.0 v / v% Phosphoric acid 7L
Was added, and the mixture was stirred for 30 minutes with a homomixer and then centrifuged to obtain a purified polycarbonate resin solution. At this time, the pH value of the aqueous layer was 2.2. 10 L of n-heptane was added to and mixed with 50 L of the purified polycarbonate resin solution, and the mixed solution was added dropwise to warm water at 45 ° C. under stirring to obtain an aqueous slurry liquid of the polycarbonate resin particles, and the temperature of the warm water was set to 1
The temperature was raised to 00 ° C., the solvent was distilled off, and filtration was performed to obtain a wet powder. The wet powder was dried at 145 ° C. for 3 hours to obtain a dry polycarbonate powder.

When the obtained powder was pelletized and a plate piece was molded, the hue YI value was 1.3.
Further, when the plate pieces were molded (retention molding test) by holding the molten resin in the cylinder for 20 minutes, the YI value of the plate was 1.4 (ΔYI = 0.1). Further, when a pellet melting test was performed, the viscosity molecular weight before melting was 21400, and the viscosity molecular weight after the melting test was 21200 (ΔMv = 200).

Example 2 In Example 1, 8 L of the acid waste water obtained in the above (2) was used.
(80% recovery) and 1.0 v / v% phosphoric acid (3 L) were added, and the same procedure as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated, except that the acid wastewater recovery rate was 9 L (90% recovery) and 1.0 v / v% phosphoric acid 3 L was added. The results are shown in Table 1.

Comparative Example 2 In Example 1, the acid wastewater was not recovered, and
Example 1 was repeated except that only 10 L of v / v% phosphoric acid was added. The results are shown in Table 1.

[0032]

[Table 1]

[0033]

EFFECT OF THE INVENTION A polycarbonate resin solution containing caustic alkali obtained by an interfacial polymerization reaction is neutralized with a mineral acid, and a part of the separated aqueous layer is recovered and reused for the neutralization reaction. As a result, the amount of mineral acid used can be reduced. Furthermore, since the polycarbonate resin produced by this method can maintain the same heat resistance and hue as the conventional method, there is no need for major process modification and the load on wastewater treatment facilities can be reduced. Its industrial significance is great.

Claims (3)

[Claims] 1. A caustic alkali obtained by a polymerization reaction in an interfacial polymerization reaction of a polycarbonate resin for carrying out a polymerization reaction by dissolving an aromatic bisphenol compound in an aqueous caustic alkali solution and carrying out a phosgenation reaction in the presence of an organic solvent. After neutralizing the resin solution by adding a mineral acid to the polycarbonate resin solution containing, the resin solution and the aqueous layer are separated, 20 to 80% (volume) of the separated aqueous layer is recovered, and A method for producing a polycarbonate resin, which is used in a sum reaction. 2. The method according to claim 1, wherein the mineral acid used for neutralization is phosphoric acid and / or phosphorous acid. 3. The method according to claim 2, wherein the mineral acid is added so that the pH value of the neutralized aqueous layer is 4 or less.