JPH0655832B2 - Method for producing polycarbonate granules - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a method for producing polycarbonate granules, more particularly continuous polycarbonate granules having a bulk density of more than 0.6 g / ml. To the manufacturing method.

<Prior Art> Various methods for producing polycarbonate granules by removing a solvent from an organic solvent solution of polycarbonate have been proposed. For example, a method of supplying a polycarbonate solution into hot water, evaporating the solvent with stirring to once form a dough, then gelling, crushing and granulating (Japanese Patent Publication No.
45-9875), 37-150 ° C. while circulating a water slurry of wet-pulverized polycarbonate granules in hot water.
A method of supplying a preheated solution of polycarbonate to a mixture under stirring to evaporate the solvent and at the same time grow particles in the slurry (JP-A-60-115625). Method to evaporate the solvent by supplying and contacting with steam (Japanese Patent Publication No. 60-54)
No. 329) is proposed.

However, in the first method, continuous production is difficult due to the phase change from the dough-like substance to the gelled substance in the container, the operation is complicated, and the thermal efficiency is remarkably poor. Moreover, the obtained granules have a wide particle size distribution and are difficult to handle. The following method is easy to make continuous, but since it is necessary to circulate a large amount of the polycarbonate granular water slurry, the production efficiency is extremely poor, and when the polycarbonate solution is preheated, especially when it is preheated to a temperature higher than the boiling point of the solvent, Easy to bump,
It becomes difficult to control steady operation. In the last method, since the purpose is to produce porous polycarbonate granules, it is necessary to keep the temperature in the container high, consume a large amount of steam, and the resulting granules are porous. Therefore, the water content is large, the drying efficiency is extremely poor, and the porous material has a low bulk density, so that the efficiency of storage, bag storage, transportation, etc. is also significantly poor.

<Object of the Invention> An object of the present invention is to continuously produce a polycarbonate particle having substantially large bulk density, which is not porous and has excellent drying efficiency and storage efficiency, storage efficiency, transportation efficiency, etc. The present invention aims to provide an efficient manufacturing method.

The present inventor, as a result of repeated intensive studies to achieve the above-mentioned object, surprisingly, when removing the solvent from the polycarbonate solution, when supplied into hot water held at a temperature specified in an extremely narrow range, Since the gelled state is directly established without passing through the rice cake state, continuous formation is facilitated, and the obtained granules have a high bulk density and are not substantially porous. I knew that I would be done. The present invention, as a result of further studies based on this finding,
It has been completed.

<Structure of the Invention> In the present invention, when continuously producing polycarbonate granules from an organic solvent solution of polycarbonate, the organic solvent solution kept at room temperature is kept at a temperature between the boiling point of the organic solvent and a temperature 5 ° C. higher than the boiling point. It is continuously fed into hot water with stirring, the organic solvent is evaporated, and the resulting gelled product of granular polycarbonate is continuously discharged out of the system without being circulated and then dried to obtain a bulk density of 0.6 g / A method for producing polycarbonate granules, characterized in that the polycarbonate granules are substantially non-porous larger than ml.

The polycarbonate referred to in the present invention is mainly a polycarbonate derived from bisphenol A.
A small proportion of other divalent phenols, such as hydroquinone,
Bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) Hexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, α, α-bis (4-hydroxyphenyl) toluene, α, α-bis (4-hydroxyphenyl) ethylbenzene, bis (4-hydroxyphenyl) Ether), bis (4-hydroxyphenyl) ketone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl)
It may be a copolymer with a sulfone or a nuclear lower alkyl-substituted product thereof.

The organic solvent used as the solvent of the polycarbonate can be arbitrarily used as long as it can dissolve the polycarbonate, for example, methylene chloride, dichlorobenzene, chloroform, tetrachloroethane, trichloroethane, dichloroethane, chlorine such as 1,2-dichloroethylene. And hydrocarbons and mixtures thereof with, for example, dioxane, tetrahydrofuran, acetophenone, toluene, xylene, cyclohexane, acetone, n-heptane and the like, and particularly, the boiling point of methylene chloride, chloroform and the like is 60.
Lower chlorinated hydrocarbons below ° C are preferred.

The organic solvent solution of the polycarbonate may be prepared by dissolving the polycarbonate in the organic solvent, but an organic solvent solution of the polycarbonate obtained by reacting a divalent phenol with phosgene in the presence of the organic solvent is preferably used. . Polycarbonate concentration in the solution is usually 7-25% by weight
The solution of polycarbonate is at room temperature, usually 10-30 ° C.
Used in.

The granulating tank used in the present invention may be any one capable of sufficiently stirring and mixing the contents, and for example, a kneader, a paddle mixer or the like is preferably used. A specific example is an apparatus as shown in FIG. In the figure, 1 is a granulation tank, 2 is a stirrer, 3 is a hot water supply pipe, 4 is an organic solvent solution supply pipe of polycarbonate, 5 is a solvent vapor discharge pipe, 6 is a discharge pipe of a slurry consisting of a gelled product of polycarbonate and hot water, and 7 Is a circulation pipe of hot water separated from the slurry, 8 is a steam supply pipe for heating the hot water, and 9 is a pump.

In the present invention, the organic solvent solution of the above-mentioned polycarbonate is continuously supplied into warm water which is maintained at a temperature between the boiling point of the solvent and a temperature higher than the boiling point by 5 ° C and which is stirred. At this time, when the temperature of the hot water is lower than the boiling point of the solvent, the evaporation rate of the solvent becomes slow, a large amount of the solvent remains in the polycarbonate in the granulation tank, and the rice cake state or the dope state is generated in the tank, and continuous production is performed. It becomes impossible. Also, if the temperature is higher than the temperature 5 ° C. higher than the boiling point of the solvent, the evaporation rate of the solvent becomes faster,
The concentration of the polycarbonate in the supplied organic solvent solution of the polycarbonate sharply rises, the time in the concentration range of 25 to 60 wt% suitable for gelling of the polycarbonate is shortened, the gelation does not proceed, and the obtained granules are obtained. Becomes porous and the object of the present invention is not achieved.

Thus, by supplying the organic solvent solution of the polycarbonate in the warm water maintained in the above temperature range and stirring and removing the solvent by evaporation, the polycarbonate does not pass through the mochi state and is directly gelled. It becomes granular. This granular material is discharged in the state of hot water slurry. The warm water is then separated and dried. During this period, the particles may be crushed to have a uniform particle size, if necessary. Any means can be adopted for this separation, drying and pulverization.

<Effects of the Invention> According to the present invention, a polycarbonate particle having substantially no bulk and large bulk density, which is excellent in drying efficiency and is also extremely excellent in efficiency of storage, bag storage, transportation, etc., is continuously prepared from a polycarbonate solution. It can be manufactured efficiently, and the effect it produces is exceptional.

<Examples> The present invention will be specifically described with reference to Examples.

Example A granulating apparatus as shown in FIG. 1 provided with a granulating tank having an internal capacity of 500 was used, and the concentration of polycarbonate was 15% by weight under stirring.
Methylene chloride solution of 10 kg / min and 80 kg of hot water of 1.5 kg / min are started, and at the same time, 2.7 kg / cm ² of steam from the hot water circulation pipe is maintained at a temperature of 40 ° C. When the supply of the hot water was started and the hot water slurry containing the granular particles of the polycarbonate in the slurry started to be discharged from the slurry discharge pipe, the supply of new hot water was stopped. The slurry discharged from the slurry discharge pipe is separated into granules and warm water by a separator, and the separated warm water is circulated and reused by a circulation pump, and at the same time, 2.7 kg / cm ² of steam is continuously supplied to the granulation tank. The temperature of the hot water inside was kept at 40 ° C.

The polycarbonate granules separated from the slurry contained 40% by weight of methylene chloride and 2% by weight of water and had a particle size of 1 to 10 mm. The granules are classified, and the granules having a particle size of 3 mm or less are dried with a hot air dryer at 145 ° C. for 4 hours to give a methylene chloride content of 0.03% by weight, a water content of 0.01% by weight, a bulk density of 0.66 g / ml, and a melting point. A granular body of 142 ° C. was obtained. When the granules were magnified 500 times with a microscope and examined, no pores were observed.

Comparative Example 1 For comparison, the same procedure as in the above Example was performed except that the temperature of the hot water in the granulation tank was changed to 60 ° C. Polycarbonate granules separated from the slurry are 15% by weight methylene chloride, 28% water.
% By weight and had a particle size of 1-10 mm. The granules were classified, and the granules with a particle size of 3 mm or less were dried with a hot air dryer at 145 ° C., and partially melted. Therefore, the granules were dried at 135 ° C., which is 2 ° C. higher than Tg, for 4 hours, and the methylene chloride content was 0.30 wt%. A granular material having a water content of 0.15% by weight and a bulk density of 0.43 g / ml was obtained. When this granular material was examined with a microscope at a magnification of 500 times, it was extremely porous, and a considerable number of large pores of about 100 μ were observed.

Comparative Example 2 For comparison, the same procedure as above was carried out except that the temperature of the hot water in the granulation tank was changed to 36 ° C. As a result, a rice cake-like or gel hydration phenomenon occurred in the granulation tank, resulting in continuous granulation. Could not be discharged.

The solid partially withdrawn from the granulation tank contained 61% by weight of methylene chloride and 5% by weight of water, and was a large lump. When dried at 145 ° C for 4 hours with a hot air dryer, the bulk density is 0.60 g / ml,
The melting point was 143 ° C.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus suitable for carrying out the present invention. In the figure, 1 is a granulation tank, 2 is a stirrer, 3 is a hot water supply pipe, 4 is an organic solvent solution supply pipe of polycarbonate, 5 is a solvent vapor discharge pipe, 6 is a discharge pipe of a slurry consisting of a gelled product of polycarbonate and hot water, and 7 Is a circulation pipe of hot water separated from the slurry, 8 is a steam supply pipe for heating the hot water, and 9 is a pump.

Claims (1)

[Claims] 1. When continuously producing polycarbonate granules from an organic solvent solution of polycarbonate, the organic solvent solution kept at room temperature is placed in warm water kept at a temperature between the boiling point of the organic solvent and a temperature 5 ° C. higher than the boiling point. It is continuously fed with stirring, the organic solvent is evaporated, and the resulting gelled product of granular polycarbonate is continuously discharged out of the system without being circulated and then dried to have a bulk density of more than 0.6 g / ml. A method for producing a polycarbonate granule, which comprises forming a polycarbonate granule that is not substantially porous.