JPH07165930A - Continuous production of polycarbonate powder - Google Patents

Abstract

PURPOSE:To provide a method for efficiently and continuously producing a polycarbonate powder, excellent in drying of polycarbonate from an organic solvent solution and capable of satisfactorily reducing the residual solvent according to the conventional drying method. CONSTITUTION:This is related to a method for producing a polycarbonate powder by continuously supplying an organic solvent solution of polycarbonate to a granulation tank accommodating hot water kept to a high temperature within a range of the boiling point of the organic solvent to a temperature >=40 deg.C higher than the boiling point with stirring and removing the organic solvent. In this production method, the generated polycarbonate powder slurry is taken out from a granulation tank, subjected to grinding treatment by using a wet grinder and subsequently classified into a powder slurry having <=0.3mm particle size and another powder slurry having a larger particle size by using a wet-type classifier. The powder slurry having a smaller particle size is recycled to a granulation tank and the other powder slurry having a larger particle size is supplied to the next process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing polycarbonate powder particles from a solution of polycarbonate in an organic solvent. More specifically, it relates to a method for efficiently and continuously producing a polycarbonate powder granule having excellent drying property from an organic solvent solution of polycarbonate and capable of sufficiently reducing the amount of residual solvent by ordinary drying.

[0002]

2. Description of the Related Art As a method for obtaining polycarbonate powder particles from an organic solvent solution of polycarbonate, an organic solvent solution of polycarbonate is supplied under stirring to a granulation tank in which hot water kept at a temperature equal to or higher than the boiling point of the organic solvent is present. The organic solvent is removed, the generated polycarbonate powder granules slurry is withdrawn from the granulation tank, pulverized by a wet pulverizer, a part of the treated slurry is supplied to the next step (dehydration, drying, etc.), and the rest is produced. A method of circulating in a grain tank is known (Japanese Patent Publication No. 4-10498, JP-A-60-115625, JP-A-60-1161212). However,
The polycarbonate powder obtained by such a method is inferior in drying property, and it is difficult to sufficiently reduce the residual solvent amount by drying. Moreover, in all of these methods, since the slurry subjected to the wet pulverization treatment is directly supplied to the next step, the content of fine powder is large, which causes a problem of hygiene during handling.
During drying, problems such as deterioration of drying efficiency and deterioration of quality due to adhesion to the machine wall are likely to occur.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to efficiently produce a polycarbonate powder from an organic solvent solution of polycarbonate which is excellent in drying property and which can sufficiently reduce the residual solvent amount by ordinary drying. Is to provide a method.

The present inventor has conducted earnest studies with the object of achieving the above object, and as a result, if the particle size of the polycarbonate powder granules present in the warm water in the granulating tank for supplying the organic solvent solution of the polycarbonate is reduced, It has been found that the dryness of the resulting product granules is remarkably improved. As a result of further study based on this knowledge, the polycarbonate powder granule slurry extracted from the granulation tank was crushed by a wet crusher, a part of the crushed slurry was supplied to the next step, and the rest was put in the granulation tank. In the circulating method, the pulverized slurry is separated by a wet classifier into a granular particle slurry having a desired particle size or less and a granular particle slurry having a larger particle size, and a granular particle slurry having a smaller particle size is formed in a granulation tank. If it is circulated, the polycarbonate powder granules with excellent drying property and a sufficiently small amount of residual solvent can be obtained by ordinary drying, and the powder granules obtained have an even particle size and a small amount of fine powder. The inventors have found that the following can be obtained and completed the present invention.

[0005]

According to the present invention, a solution of a polycarbonate in an organic solvent is prepared from the boiling point of the organic solvent to the boiling point of the organic solvent.
When the polycarbonate powder granules are produced by continuously supplying to a granulation tank containing warm water maintained at a high temperature of 0 ° C. under stirring and removing the organic solvent to produce the polycarbonate powder granules. It is extracted from the powder, pulverized by a wet pulverizer, and then separated by a wet classifier into a granular slurry with a particle size of 0.5 mm or less and a granular slurry with a larger particle size, and a granular particle slurry with a smaller particle size is obtained. Circulate in the granulation tank,
This is a continuous production method for polycarbonate powder or granules, characterized in that the powder or granule slurry having a large particle size is supplied to the next step.

The present invention will be described below with reference to the drawings. Figure 1
1 is a system diagram showing an example of an apparatus suitable for carrying out the present invention. In the figure, 1 is a polycarbonate organic solvent solution introducing pipe, 2 is a granulating tank, 3 is a stirrer, 4 is a water supply pipe, 5 Is an organic solvent vapor discharge pipe, 6 is a steam blowing pipe for heating, and 7 is
Is a pipe for extracting the polycarbonate powder granule slurry, 8 is a wet pulverizer, 9 is a conduit for circulating slurry, 10 is an introducing pipe to a wet classifier, 11 is a wet classifier, 12 is a conduit for circulating slurry after classification, 13 is a pipe for extracting the slurry after classification, a, b
And c are valves.

In the granulation tank 2, the polycarbonate powder granule slurry extracted from the extraction pipe 7 is pulverized by the wet pulverizer 8 and then by the wet classifier 11 the powder granule slurry having a desired particle size or less and the desired particle slurries are obtained. Separate the powdery slurry with a particle size larger than the particle size, circulate and supply the separated powdery slurry with a small particle size, and water from the replenishment pipe 4 and the steam from the blowing pipe 6 so as to reach a predetermined amount and temperature. To supply. The polycarbonate organic solvent solution is continuously stirred and supplied from the introduction pipe 1 to the hot water slurry of the polycarbonate powder in the granulation tank 2 which is maintained at a predetermined amount and temperature, and the evaporated organic solvent is discharged from the discharge pipe 5. Further, the polycarbonate powder granules that have been discharged to the outside of the system and continuously grown are extracted as a slurry from the extraction pipe 7, pulverized by the wet pulverizer 8 and then pulverized by the wet classifier 11 to form a granular particle slurry having a desired particle size or less. The granular particle slurry having a particle size larger than a desired particle size is separated, the granular particle slurry having a smaller particle size is circulated in the granulation tank 2, and the granular particle slurry having a larger particle size is subjected to the next step, for example, a dehydration step or a dewatering step. Supply to the solvent process.

In the above method, at the time of start-up, the valve a is opened, the valves b and c are closed, a predetermined amount of water is charged in the granulation tank 2, and the extraction tube 7 and wet pulverization are performed while heating with steam. Circulated by machine 8 and circulating slurry conduit 9,
When the water reaches a predetermined temperature, the polycarbonate organic solvent solution is supplied with stirring, the generated organic solvent vapor is discharged through the discharge pipe 5, and the generated polycarbonate powder granule slurry is circulated while being crushed by the wet crusher 8. Let
During this period, the temperature is maintained at a predetermined temperature by steam. When the powder or granular material in the slurry reaches a predetermined concentration, the valves b and c are opened and the valve a is closed to start the steady operation. Also,
It is also possible to start up with a slurry in a steady operation state using a polycarbonate powder produced in advance.

The polycarbonate which is the object of the present invention is
Although it may be produced by any method, the phosgene method in which the product is obtained as an organic solvent solution is preferable. The phosgene method is a well known method, in which an oligomer obtained by reacting phosgene with an alkaline aqueous solution of a dihydric phenol in the presence or absence of an organic solvent is subjected to a polymerization reaction in the presence of an organic solvent to give a polycarbonate. Obtained as an organic solvent solution. In this method, if necessary, a catalyst,
A terminal stopper, a dihydric phenol antioxidant, and other additives can be used. Further, the obtained polycarbonate may be, for example, a branched polycarbonate obtained by reacting a trifunctional or higher polyfunctional aromatic compound, a mixture of two or more kinds of polycarbonate, or a polyester carbonate. The degree of polymerization of the polycarbonate does not need to be particularly limited as long as it becomes a slurry. Usually, those having a viscosity average molecular weight of 13,000 or more are used.

The dihydric phenol used here has the following general formula

[0011]

[Chemical 1]

[Wherein, R is a divalent alkylidene group having 1 to 15 carbon atoms, a phenyl-substituted alkylidene group, a cycloalkylidene group, an alkylene group,>S,>O,> S = O,>
SO ₂ or> CO, X ₁ and X ₂ are alkyl groups or halogen atoms, and X ₁ and X ₂ may be the same or different. m and n are 0, 1 or 2. ], 2,2-bis (4-
Hydroxyphenyl) propane (commonly called bisphenol A) is preferably used, and other dihydric phenols include, for example, bis (4-hydroxyphenyl) methane,
1,1-bis (4-hydroxyphenyl) ethane, 1,
1-bis (4-hydroxyphenyl) cyclohexane,
2,2-bis (4-hydroxy-3-methylphenyl)
Propane, bis (4-hydroxyphenyl) sulfone,
Examples thereof include bis (4-hydroxyphenyl) ether and the like, and halogenated bisphenols such as 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane. These may be used alone or in combination of two or more.

The organic solvent used in the present invention is WFCHRISTO
"Polycarbonates" 1962 by PHER, DWFOX, "Good Solvents" and "Fair Solvent" in Table 3-1 on page 32
The solvent corresponding to "s" is, for example, ethane tetrachloride, methylene chloride, 1,2-dichloroethylene, chloroform, dioxane, tetrahydrofuran or the like alone or in a mixed solvent.

The concentration of the polycarbonate dissolved in the above organic solvent is not particularly limited, but is usually 3 to 40% by weight, preferably 5 to 30% by weight. This concentration is 3
If it is less than 10% by weight, the amount of the solvent to be recovered increases, resulting in reduced productivity and inefficiency. On the other hand, if it exceeds 40% by weight, it solidifies and becomes difficult to supply to the granulation tank.

In the granulation tank into which the organic solvent solution of polycarbonate is introduced, there are warm water and a polycarbonate powder which are kept at a temperature between the boiling point of the organic solvent and a temperature 40 ° C. higher than the boiling point. A water slurry of the grown polycarbonate powder is produced by dropping, flowing or directly introducing into hot water and evaporating and removing the organic solvent. The organic solvent solution to be introduced may be at room temperature or may be heated in advance. If the temperature of the hot water in the granulation tank is lower than the boiling point of the organic solvent, the evaporation of the organic solvent is slow and inefficient, and if the temperature exceeds 40 ° C. higher than the boiling point, the bulk density of the obtained granular material decreases. So not suitable. The granulating tank may be any device capable of heating and stirring, and a stirring tank is usually used.

The polycarbonate powder / water ratio (polycarbonate / water) in the granulation tank is preferably 0.03 to 0.5 in terms of polycarbonate dry base weight ratio in terms of handling slurry such as stirring and circulation. Especially 0.05 ~
0.35 is preferable. The ratio of the polycarbonate powder and water is preferably kept in the above range by adjusting the amount of the polycarbonate organic solvent solution introduced into the granulation tank, the amount of makeup water, and the amount of the slurry extracted after classification.

An aqueous slurry of the polycarbonate powder granules grown from the granulation tank is taken out and pulverized by a wet pulverizer. As the wet crusher, a wet crusher having a transportation function is suitable. For example, if it is a commercially available product, a disintegrator manufactured by Komatsu Zenoa Co., Ltd., a Gorator manufactured by Nittetsu Mining Co., Ltd., or Mitsui Miike Kakoki Co., Ltd. Trade names such as Trigonal can be cited. Further, it does not matter if the pump and the crusher are used together. The polycarbonate powder particles in the crushed slurry do not have a uniform particle size and contain a large amount of fine powder that is difficult to handle.

In the present invention, this large amount of fine powder is skillfully utilized to obtain a polycarbonate powder granule having excellent dryability and having a sufficiently small amount of residual solvent by ordinary drying. That is, a polycarbonate powder granule slurry containing a large amount of pulverized fine powder is separated by a wet classifier into a polycarbonate powder granule slurry having a desired particle size or smaller and a polycarbonate powder granule slurry having a larger particle size than a desired particle size, The polycarbonate powder granules having a particle size or less is circulated in the granulation tank, and grown again in the granulation tank.

The desired particle size in the present invention is 0.3 mm or less. When a slurry of polycarbonate powder particles having a particle size of more than 0.3 mm is circulated in the granulation tank, it is difficult to obtain the desired powder particles having excellent dryness. Moreover, although some fine powder adheres to the resulting product granules, it does not substantially contain powder of 0.3 mm or less, so its handleability is good, and drying due to adhesion to the machine wall during drying is possible. Problems such as reduced efficiency and deteriorated quality are unlikely to occur. Proportion of powdery or granular material slurry having a particle size equal to or smaller than the desired particle size and powdery or granular material slurry having a particle size larger than the desired particle diameter, that is, the powder or granular material slurry circulated in the granulation tank 2 and the powder or granular material slurry supplied to the next step The ratio is usually 1: 9 to 8: 2, preferably 2: 8 to 5: 5, and can be easily adjusted by setting the wet pulverizer and the wet classifier. Any type of wet classifier can be used, for example, a wire mesh filter can be used, but a wet cyclone is preferably used.

[0020]

EXAMPLES The present invention will be further described with reference to the following examples. In addition,% in the examples is% by weight, and evaluation was performed by the following method. (a) Chlorine content (ppm): Determined by analysis with a total organic halogen analyzer [TOX manufactured by Mitsubishi Kasei Co., Ltd.]. (b) Average particle size (mm) and particle size distribution (n): Measured in accordance with the particle size measurement method described in Chapter 2, Section 2.4, "Granulation Handbook" edited by Japan Powder Industry Association. The n in the Rosin-Rammler formula serves as a guide for the particle size distribution, and the larger the value, the narrower the width of the particle size distribution. (c) Adhesion to dryer wall: Visually observe the degree of adhesion, and a large amount indicates a large amount of adhesion, and a small amount does not affect the drying efficiency, but a small amount adheres to drying. The case where there is no actual damage to the efficiency is shown as small, and the case where there is almost no adhesion is shown as minute, and the cases of minute and small are regarded as acceptable.

[Embodiment 1] Using the apparatus shown in FIG. 1, an agitator tank having an inner diameter of 80 cm and a capacity of 450 liters was equipped with an agitator 3 of three turbine blades having an impeller diameter of 70 cm and an impeller width of 10 cm in a granulating tank 2. The wet pulverizer 8 used was a trademark of Mitsui Miike Kakoki Co., Ltd. Trigonal, and the wet classifier 11 had a cylindrical inner diameter of 75 mm.
A wet cyclone having a feed connection pipe diameter of 50 mm and an overflow connection pipe diameter of 50 mm was used. As a polycarbonate solution, a 15% methylene chloride solution of polycarbonate having a viscosity average molecular weight of 23,500 obtained from bisphenol A and phosgene by a conventional method was used. The valve a is opened, the valves b and c are closed, 300 liters of water at 43 ° C. is charged into the granulation tank 2, and steam is blown from the blow-in pipe 6 to adjust the water temperature in the granulation tank 2 to 43 ° C.
While maintaining the temperature at 100 ° C. and stirring at 100 rpm, the polycarbonate solution was continuously introduced at 300 kg / hour through the introduction tube 1 to evaporate methylene chloride, and the produced polycarbonate powder granule slurry was discharged from the extraction tube 7 at 3000 liters / hour. It was taken out, pulverized by the wet pulverizer 8 and circulated through the circulation slurry conduit 9 into the granulation tank 2. One hour after starting the introduction of the polycarbonate solution, the valves b and c were opened, the valve a was closed, and the pulverized slurry was treated with a wet classifier 1 through a classifier introduction tube 10.
1 and classification treatment is performed, and a slurry of polycarbonate powder or granules having a particle diameter of 0.3 mm or less is circulated to the granulation tank 2 through the circulation slurry conduit 12 to obtain a slurry of polycarbonate powder or granules having a particle diameter of 0.3 mm or more. From the slurry extraction pipe 13 1
It was withdrawn at 50 liters / hour. On the other hand, water was replenished from the water replenishment pipe 4 to maintain the inner volume of the granulation tank 2 at 300 liters. The weight ratio (polycarbonate / water) of polycarbonate powder and water of the extracted slurry was 0.3. Polycarbonate powder and granules were separated from the extracted slurry by a centrifuge and dried by a paddle dryer at 145 ° C. for 6 hours, and the evaluation results are shown in Table 1. After continuous operation for 10 days in this manner, there was no abnormality and no change in product quality.

Example 2 A polycarbonate powder was obtained in the same manner as in Example 1 except that the water temperature in the granulation tank 2 was maintained at 70 ° C. The evaluation results are shown in Table 1.

[Comparative Example 1] One hour after the start of introduction of the polycarbonate solution, the valves a and b were opened, the valve c was closed, and 150 liters / hour of slurry was circulated through the classifier introduction pipe 10 and the wet classifier 11. A polycarbonate powder was obtained in the same manner as in Example 1 except that the powder was extracted from the slurry extraction tube 13 without classification. The evaluation results are shown in Table 1.

[Comparative Example 2] 1 hour after the start of introduction of the polycarbonate solution, the valves a and b were opened, the valve c was closed, and 150 liters / hour of slurry was circulated through the classifier introduction pipe 10 and the wet classifier 11. A polycarbonate powder was obtained in the same manner as in Example 2 except that the powder was extracted from the slurry extraction tube 13 without classification. The evaluation results are shown in Table 1.

[0025]

[Table 1]

[0026]

EFFECTS OF THE INVENTION According to the method of the present invention, polycarbonate powder particles having excellent dryability, uniform particle size and little fine powder, excellent handleability and hygiene due to dust generation, and having little adhesion of fine powder to the dryer wall The body can be manufactured efficiently, and the industrial effect that it produces is exceptional.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an apparatus suitable for carrying out the present invention.

[Explanation of symbols]

 1 Polycarbonate solution introduction pipe 2 Granulation tank 3 Stirrer 4 Water supply pipe 5 Solvent vapor discharge pipe 6 Steam blow-in pipe 7 Slurry extraction pipe 8 Wet grinder 9 Circulating slurry conduit 10 Classifier introduction pipe 11 Wet classifier 12 After classification Circulation slurry conduit 13 Slurry withdrawal pipe after classification a, b and c valves

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshifumi Ikemura 1-6-21 Nishishinbashi, Minato-ku, Tokyo Inside Teijin Kasei Co., Ltd.

Claims (1)

[Claims] 1. An organic solvent solution of polycarbonate is continuously supplied with stirring to a granulation tank in which warm water is maintained at a temperature between the boiling point of the organic solvent and a temperature 40 ° C. higher than the boiling point, and the organic solvent is removed to remove the polycarbonate. When manufacturing powder and granules,
The generated polycarbonate powder granules slurry is extracted from the granulation tank, pulverized by a wet pulverizer, and then separated by a wet classifier into a powder granule slurry having a particle diameter of 0.3 mm or less and a granule slurry having a larger particle diameter. Then, a method for continuously producing a polycarbonate powder or granular material, characterized in that the powder or granular material slurry having a small particle diameter is circulated in a granulation tank, and the powder or granular material slurry having a large particle diameter is supplied to the next step.