JP3182327B2 - Method for producing purified polycarbonate solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a purified polycarbonate solution, and more particularly to a method for efficiently producing a purified polycarbonate solution from which impurities are effectively removed and whose quality is improved.

[0002]

2. Description of the Related Art At present, as a method for producing polycarbonate, a production method by an interfacial polycondensation method (so-called phosgene method) using methylene chloride as a solvent is widely practiced. In this method, a polymer solution (crude polycarbonate solution) containing a large amount of impurities is obtained after completion of the polycondensation reaction. Therefore, various cleaning methods in many steps are being studied. Normally, a purified polycarbonate solution is obtained by washing the crude polycarbonate solution with alkaline water, acidic water, pure water, etc., and further separating and removing the washing water by centrifugation, stationary separation, or the like. The supersaturated water in the solution could not be completely removed.

[0003] The supersaturated water contained in the polycarbonate solution contains many impurities which adversely affect the physical properties of the polycarbonate. Reducing it will improve the quality of the polycarbonate.

[0004] Separation using a centrifugal separator or the like is effective for separating a mixture of a polycarbonate solution and washing water. However, stationary separation is often employed in terms of equipment cost. However, in any of the separations, the supersaturated water in the polycarbonate solution could not be completely removed, and consequently, impurities that had an adverse effect on the physical properties of the polycarbonate could not be completely removed.

[0005] As a method of removing impurities contained in such a polycarbonate solution, a reaction solution containing polycarbonate obtained by the phosgene method is passed through a first filter medium layer to form giant water droplets, and then from a hydrophobic filter medium. A method of removing an aqueous phase by contacting a second filter medium layer and passing only a polycarbonate solution has been proposed (Japanese Patent Publication No. 59-22733). According to this method, although the water-soluble impurities contained in the organic phase can be removed, there is a disadvantage that the filter medium layer has a small pore diameter and the amount of liquid that can pass therethrough is small, so that the equipment becomes large.

[0006] Further, in a method for producing a polycarbonate in which an aqueous phase is removed from a reaction solution containing a polycarbonate obtained by a phosgene method and then the polycarbonate is isolated from an organic solvent, a polytetrafluoroethylene-made filter medium layer is provided.
A method has been proposed in which the above-mentioned aqueous phase is removed after passing the above-mentioned reaction solution comprising polycarbonate, water, an organic solvent and impurities (Japanese Patent Publication No. 59-29603).
However, in the case of this method, there is a problem that it takes a long time to perform the filtration because the reaction solution is directly passed through the filter medium layer without being separated by standing. In addition, as in the above method, this method has a disadvantage that the filter medium layer has a small pore diameter and a small amount of liquid can pass therethrough, so that the equipment becomes large. Furthermore, because of the filtration of the organic and aqueous phase mixture,
There are drawbacks such as insufficient removal of supersaturated water in the organic phase and insufficient removal of impurities.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional disadvantages, and effectively removes impurities contained in a polycarbonate solution, especially in its supersaturated water,
It is an object of the present invention to provide a method for efficiently producing a purified polycarbonate solution with improved quality.

[0008]

That is, the present invention provides a method for producing a purified polycarbonate solution by washing a crude polycarbonate solution which has been subjected to a polycondensation reaction by an interfacial polycondensation method. After washing the finished crude polycarbonate solution with washing water under stirring, the crude polycarbonate solution containing washing water is separated into an aqueous phase and an organic phase containing polycarbonate by standing separation or centrifugation, and then the polycarbonate is separated. The organic phase containing the organic phase was filtered using a filtration filter having a pore size of 20 to 180 μm and a filtration flow rate of 60 to 1000 mm / mi.
It is intended to provide a method for producing a purified polycarbonate solution, characterized by filtering under a condition of n.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to the drawings. FIG. 1 is a flow sheet of the method of the present invention.

The crude polycarbonate solution used in the method of the present invention is obtained by a polycondensation reaction by an interfacial polycondensation method (phosgene method), and is dissolved in an organic solvent substantially insoluble in water as a solvent. It is in the state. Such a crude polycarbonate solution can be obtained, for example, by adding methylene chloride as a solvent to an aqueous solution of bisphenol A and blowing phosgene with stirring to advance and complete the polycondensation reaction. The conditions for this polycondensation reaction may be performed according to a conventional method.

As the polycarbonate used in the method of the present invention, a branched polycarbonate, a halogen-type polycarbonate containing bromine or chlorine, and other comonomers are used in addition to a normal-type polycarbonate mainly made of bisphenol A. Special polycarbonate such as copolymerized polycarbonate may be used. An organic solvent substantially insoluble in water is used as the solvent.
Specifically, for example, chlorinated hydrocarbons such as methylene chloride and chloroethane, aromatic solvents such as chlorobenzene,
It can be used alone or as a mixed solvent.

The molecular weight of the polycarbonate to be produced is not particularly limited as long as it can be handled as a solution. Usually, the viscosity-average molecular weight Mv = 1000 to 100,
000 (-), preferably Mv = 2000 to 50,000
0 (-).

The concentration of the polycarbonate solution is usually 30% by weight or less, preferably 25% by weight or less. If it exceeds 30% by weight, the viscosity of the solution is too high, which is not preferable. However, this does not apply to the case where the viscosity is relatively reduced by pressurizing and heating.

At the end of the polycondensation reaction, the crude polycarbonate solution usually contains, in addition to polycarbonate, water and an organic solvent, phenols (eg, bisphenol A and paratertiary butylphenol) as unreacted monomers, It contains impurities such as sodium hydroxide as alkali, tertiary or quaternary ammonium salts used as catalysts (eg, triethylamine), and salts of by-products of polymerization (eg, sodium chloride).

In order to remove these impurities, washing with washing water is carried out. Generally, water or alkaline water is used for removing unreacted monomers, acidic water is used for removing catalyst and alkali, and salts and alkali are used for removing catalyst and alkali. Pure water is used for the removal.

In the method of the present invention, the crude polycarbonate solution having been subjected to the polycondensation reaction by the interfacial polycondensation method as described above is first washed with washing water with stirring. Here, for the washing with washing water, washing water can be selected according to the raw materials used in the interfacial polycondensation method. Accordingly, there is a case where either one of water-alkaline water and acidic water or a combination of washing steps using any two kinds of washing water or a combination of washing steps using three kinds of washing water is used. Is applicable to both cases.

When a washing solution selected for the purpose of washing is added to and mixed with the crude polycarbonate solution and washed with stirring, stirring power Pv = 0.1 (KW / [m ³ / hr]) or more, preferably 0.5 ２2 (KW / [m ³ / hr]). Here, if the stirring power Pv is less than 0.1 (KW / [m ³ / hr]), a predetermined cleaning effect cannot be obtained, which is not preferable. In addition, the phase of the crude polycarbonate solution and the water is performed in a normal phase.

The volume of water in the mixed solution is 1
It is 50 vol%, preferably 5-40 vol%.
If the volume of water is less than 1 vol%, the amount of washing water is small relative to the crude polycarbonate solution, and the effect of washing is not exhibited. When the volume of water exceeds 50 vol%, it is generally difficult to maintain a normal phase. Generally, a method in which a small amount of a washing liquid is added first to form a normal phase, and then washing water is added, so that the water phase ratio can be easily increased.

As a device for stirring the crude polycarbonate solution and the washing water (stirring mixer 1 in FIG. 1), any device used for the liquid-liquid stirring and mixing can be used. In this respect, an in-line mixer, a static mixer, an orifice and the like are suitable in addition to the ordinary stirring tank.

Next, as a first stage separation, a mixture of the crude polycarbonate solution and the washing water (crude polycarbonate solution containing the washing water), which has been stirred and mixed by the stirring mixer 1 as described above, is separated by standing or centrifugation. By the separation, an aqueous phase and an organic phase containing polycarbonate are separated. In FIG. 1, reference numeral 2 denotes a stationary separation tank or a centrifuge.

In the organic phase containing polycarbonate separated by the first-stage separation (static separation or centrifugation), a trace amount of water that cannot be separated exists. In addition, complete separation of the crude polycarbonate solution and the washing water (that is,
Separation up to the saturated water content) can be dealt with by increasing the standing time in a stationary separation tank and by increasing the number of revolutions in a centrifuge, but there are problems such as equipment performance and equipment costs. Therefore, recruitment is practically impossible.

For this reason, as a second stage separation, the organic phase containing the polycarbonate is filtered at a specific filtration flow rate using a specific filtration filter to obtain a trace amount of water (the organic phase contained in the polycarbonate-containing organic phase). Supersaturated water). In FIG. 1, reference numeral 3 denotes a filtration filter.

Here, the material of the filtration filter 3 is not particularly limited, but is usually selected from the group consisting of polyethylene, polypropylene, diatomaceous earth, filter paper and polytetrafluoroethylene, and particularly polypropylene, polytetrafluoroethylene. Ethylene is preferred. The pore size of the filter 3 is 20 to 180 μm, preferably 50 to 100 μm.

Here, a line filter is used as the filtration filter 3 . The filtration flow rate is 60 to 10
00 mm / min, preferably 300 to 800 mm / m
It is necessary to set to in. Filtration flow rate is 60mm / m
If it is slower than in, the flow rate per filter increases, and the equipment becomes large. On the other hand, the filtration flow rate is 1000 mm
If it is faster than / min, the efficiency of removing impurities is reduced. In order to secure the filtration flow rate as described above, a pump 4 or the like may be used as necessary.

By the above operation, the amount of water in the purified polycarbonate solution reaches a saturated amount, and a clear purified polycarbonate solution containing few impurities can be obtained. Separated water discharged at the time of passage through the filtration filter can be effectively used by being recycled to the stationary separation tank or the inlet of the centrifuge 2.

As described above, a desired purified polycarbonate solution can be obtained. The organic solvent (such as methylene chloride) is removed by evaporating and concentrating the purified polycarbonate solution according to a conventional method to obtain a polycarbonate. That is, by removing the organic solvent from the purified polycarbonate solution, a polycarbonate useful as a so-called engineering plastic can be obtained. Instead of evaporating and concentrating and drying, the polycarbonate can be precipitated and isolated by using an organic solvent (eg, acetone or the like) that does not dissolve the polycarbonate but dissolves the used organic solvent.

[0027]

Next, the present invention will be described in more detail with reference to examples, but the scope of the present invention is not limited thereby.

Example 1 (1) Production of crude polycarbonate solution A polycarbonate synthesis reaction was carried out by an interfacial polycondensation method using methylene chloride, bisphenol A and phosgene, and the final polycarbonate emulsion was centrifuged to obtain bisphenol. A: A crude polycarbonate solution containing 31 (wt-ppm) and 45 (wt-ppm) triethylamine (polycarbonate viscosity average molecular weight Mv =
26500, concentration 25.0 wt%).

(2) Washing In order to wash this solution with alkaline water, pH = 1
A caustic soda solution adjusted to 2.5 was used, and the crude polycarbonate solution phase was 80 vol% and the aqueous phase was 20 vol.
200 (liter / hr), 5
At a feed rate of 0 (liter / hr), a pipeline homomixer as a stirring and mixing machine 1 (Tokusai Kika Kogyo Co., Ltd.)
And washed with stirring under the condition of a stirring intensity of 0.6 (KW [m ³ / hr]).

(3) Separation in First Step (Centrifugal Separation) Next, a mixture of the crude polycarbonate solution and the washing water (the crude polycarbonate solution containing the washing water) stirred and mixed by the stirring mixer 1 as described above is When the aqueous phase and the organic phase containing polycarbonate were separated using a centrifuge (Ultrex UEM90 manufactured by Hitachi, Ltd.), the water content in the organic phase containing polycarbonate was 3500 (wt-p).
pm).

(4) Separation in Second Step (Filtration by Filtration Filter) Further, the organic phase containing the polycarbonate after the centrifugation is filtered at a feed rate of 3 (liter / min) using a filtration filter 3 (made of polypropylene) having a pore diameter of 20 μm. And filtered at a filtration flow rate shown in Table 1 to obtain a purified polycarbonate solution. The amount of water in the purified polycarbonate solution was measured and found to be 2200 (wt-ppm). At this time, the saturated water content of methylene chloride at the temperature of the purified polycarbonate solution was 2170 (wt-ppm), and it was confirmed that the supersaturated water content in the purified polycarbonate solution was removed. In addition, as a result of measuring the amount of residual bisphenol A and the like, it was confirmed that the amount of residual bisphenol A was sufficiently reduced. Table 1 shows the results.

Example 2 In Example 1, the amount of triethylamine in the crude polycarbonate solution which was filtered after washing with alkaline water was 32 (wt-ppm). The solution was further washed with acid. I decided that. As washing water, acidic water adjusted to pH = 2 with hydrochloric acid was used. When the polymer solution after washing was separated into an aqueous phase and an organic phase containing polycarbonate in a stationary separation tank, the water content in the organic phase containing polycarbonate was 4000 (wt-ppm). The organic phase containing the polycarbonate after the standing separation was filtered at a feed rate of 3 (liter / min) using a filtration filter 3 having a pore size of 20 μm.
(Made of polypropylene), and filtered at a filtration flow rate shown in Table 1 to obtain a purified polycarbonate solution. When the water content in this purified polycarbonate solution was measured,
2200 (wt-ppm), confirming that the supersaturated water content in the purified polycarbonate solution was removed. In addition, as a result of measuring the amount of residual bisphenol A and the like, it was confirmed that the amount of residual bisphenol A was sufficiently reduced. Table 1 shows the results.

Example 3 In Example 2, the amounts of Na and Fe in the crude polycarbonate solution which was filtered after washing with an acid were measured, and were 1 (wt-ppm) and 0.8 (wt-ppm), respectively. And
The crude polycarbonate solution was further washed with pure water. When the polymer solution after washing with pure water was separated into an aqueous phase and an organic phase containing polycarbonate in a stationary separation tank, the water content in the organic phase containing polycarbonate was 3,500 (wt-ppm). The organic phase containing the polycarbonate after the standing separation was added to 3 (liter / liter).
through a filtration filter 3 (made of polypropylene) having a pore diameter of 20 μm at a supply speed of (min), and filtered at a filtration flow rate shown in Table 1 to obtain a purified polycarbonate solution. When the amount of water in this purified polycarbonate solution was measured,
00 (wt-ppm), confirming that the supersaturated water content in the purified polycarbonate solution was removed. Also,
As a result of measuring the amount of residual bisphenol A and the like, it was confirmed that the amount of residual bisphenol A was sufficiently reduced. Table 1 shows the results. Further, the residual N
As a result of measuring the amount of a and the amount of residual Fe, it was confirmed that both the amount of residual Na and the amount of residual Fe were sufficiently removed.

Examples 4 and 5 and Comparative Example 1 The procedure of Example 1 was repeated, except that the pore size of the filter was changed to the size shown in Table 1, and the same evaluation was performed. . The results are shown in Table 1.

Example 6 and Comparative Example 2 The procedure of Example 1 was repeated, except that the filtration flow rate was as shown in Table 1, and the same evaluation was performed. The results are shown in Table 1.

Examples 7 and 8 The procedure of Example 2 was repeated, except that the pore size of the filtration filter was changed to the size shown in Table 1, and evaluated in the same manner. The results are shown in Table 1.

Examples 9 and 10 The procedure of Example 3 was repeated, except that the pore size of the filter was changed to the size shown in Table 1, and the evaluation was performed in the same manner. The results are shown in Table 1.

Comparative Example 3 The procedure of Example 1 was repeated, except that no filtration filter was used, and the same evaluation was performed. The results are shown in Table 1.

[0039]

[Table 1]

[0040]

According to the method of the present invention, impurities contained in a polycarbonate solution, particularly in its supersaturated water, are effectively removed, and a purified polycarbonate solution having improved quality can be efficiently produced. .

That is, according to the method of the present invention, after the crude polycarbonate solution is washed with washing water under stirring, the crude polycarbonate solution containing the washing water is separated by standing or centrifugation, and then the separated polycarbonate is separated. The organic phase containing is filtered using a specific filtration filter and at a specific filtration flow rate, whereby supersaturated water in the organic phase is removed, and as a result, impurities in the supersaturated water can be effectively removed. .

Further, according to the method of the present invention, since a specific filtration filter is used, it is possible to perform filtration at a much higher filtration rate than in the past. In addition, the method of the present invention can be implemented with a relatively simple device, and thus has the advantage of reducing equipment costs.

Therefore, according to the method of the present invention, it is possible to finally obtain a polycarbonate in which impurities in the polycarbonate are removed and quality is improved.

[Brief description of the drawings]

FIG. 1 is a flow sheet of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stirring mixer 2 Stationary separation tank or centrifugal separator 3 Filtration filter 4 Pump

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-169822 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 64/00-64/42 C08J 3 / 00

Claims (3)

(57) [Claims] Claims: 1. A method for producing a purified polycarbonate solution by washing a crude polycarbonate solution having undergone a polycondensation reaction by an interfacial polycondensation method, comprising washing the crude polycarbonate solution having undergone a polycondensation reaction by an interfacial polycondensation method with washing water. After washing under stirring, the crude polycarbonate solution containing the washing water is separated into a water phase and an organic phase containing polycarbonate by standing separation or centrifugation, and then the organic phase containing polycarbonate is subjected to a pore size of 20 to 18
Using a filtration filter of 0 μm and a filtration flow rate of 60 to 1
A method for producing a purified polycarbonate solution, characterized by filtering under a condition of 000 mm / min. 2. The method according to claim 1, wherein the washing water is any one of water, alkaline water and acidic water, or a combination of any two or three of them. 3. The washing under stirring is performed with a stirring power of 0.1 (KW / [m
³ / hr]) or more.