JPH085965B2 - Method for producing polycarbonate powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polycarbonate powder, and more particularly to a method for producing polycarbonate powder from a solution of polycarbonate in an organic solvent.

[0002]

2. Description of the Related Art Various methods have been developed as a method for producing a polycarbonate powder from a solution of a polycarbonate in an organic solvent (generally methylene chloride). One of the methods is to concentrate the obtained organic solvent solution. A polycarbonate flake is obtained by drying, the polycarbonate flake is pre-dried at a flake temperature of 100 to 140 ° C., and then pulverized to obtain a pulverized product.
There is a method of producing a polycarbonate powder by drying at a flake temperature of 40 ° C. The above-mentioned pulverization in this method is generally carried out by a pulverizer after predrying as it is, that is, at a high flake temperature of 100 to 140 ° C.

[0003]

However, in the conventional method in which the flakes after pre-drying are crushed at a high flake temperature of 100 to 140 ° C., the flakes are crushed with high efficiency while giving priority to productivity, that is, crushing. When the unit work of the machine and the amount of treatment per unit time are increased, the ratio of the pulverized product which is difficult to dry (the pulverized product having a particle size larger than 14 mesh) in the obtained polycarbonate pulverized product increases, There is a problem that the amount of residual organic solvent in the polycarbonate powder thus obtained increases. A product using a polycarbonate powder having a large amount of residual organic solvent as a material has a drawback that the color tone and thermal stability are likely to be lower than a product using a polycarbonate powder having a small amount of residual organic solvent as a material. From the viewpoint of improving the color tone and heat stability of the product, it is preferable to make the ratio of the pulverized product which is difficult to dry in the polycarbonate pulverized product as low as possible (for example, 5% by weight or less). In order to reduce the ratio of difficultly pulverized products, it is necessary to pulverize the flakes with low efficiency, which causes a problem that productivity is reduced.

Therefore, it is an object of the present invention to provide a method for producing a polycarbonate powder which can produce a polycarbonate powder having a small amount of residual organic solvent with higher productivity than the conventional method.

[0005]

The method for producing a polycarbonate powder of the present invention which achieves the above objects, comprises concentrating and pulverizing an organic solvent solution of polycarbonate to obtain a polycarbonate flake, preliminarily drying the polycarbonate flake and then pulverizing the same. In producing a polycarbonate powder by drying the obtained pulverized product, 10 to 60 of the polycarbonate flakes after the preliminary drying are prepared.
It is characterized by crushing at a flake temperature in the range of ° C.

The present invention will be described in detail below. In the method of the present invention, the means for obtaining polycarbonate flakes by concentrating and pulverizing an organic solvent solution of polycarbonate is not particularly limited, and is applied when industrially producing polycarbonate powder by an interfacial polycondensation process. Various conventional methods can be applied as they are. The means for predrying the polycarbonate flakes is also not particularly limited, but 10
It is dried at a flake temperature of 0 to 140 ° C. so that the amount of residual organic solvent in the flakes after predrying is in the range of 0.1 to 30% by weight, particularly 0.1 to 10% by weight. Is preferred. If the amount of residual organic solvent in the flakes after predrying exceeds 30% by weight, it becomes difficult to grind. The flakes thus obtained (preliminarily dried) contain flakes having a particle size larger than 14 mesh in an amount of 10% by weight or more, usually 35 to 60% by weight.

In the method of the present invention, the flakes (preliminarily dried) thus obtained are ground at a flake temperature within the range of 10 to 60 ° C. to obtain a ground product. Here, the means for controlling the temperature of the flakes after pre-drying to 10 to 60 ° C. is not particularly limited, but industrially, after the pre-drying, the flakes are cooled by a stirring chiller with a jacket or the like. It is preferable to forcibly cool at a rate of 1 to 4 ° C./second. A large-scale cooling facility is required to keep the flake temperature below 10 ° C. Further, when the flake temperature exceeds 60 ° C, in order to reduce the proportion of the pulverized product which is difficult to dry in the polycarbonate pulverized product, the flakes must be pulverized at a level extremely lower than the maximum processing capacity of the pulverizer. , Productivity is reduced. Particularly preferable flake temperature (milling material temperature) during milling is 1
It is 0-40 degreeC.

The crushing means in the method of the present invention is not particularly limited as long as it is a means other than the wet method, and an air flow type crusher or an impact type crusher can be applied as in the conventional method, and particularly, an impact type. A crusher is preferably used. Examples of the impact type crusher include a free crusher, a parallelizer, a coloplex mill, an impact mill, a parbacron, a palman mill, a micro pad, a vertical mill, a micron dryer, a super micron mill, an atomizer, a turbo mill, and a micro cyclomat. Any impact crusher can be used. When the flake temperature during crushing may exceed 60 ° C. due to shear friction heat or the like, it is preferable to use a crusher having a jacket or a rotor with a cooling mechanism.

Grinding conditions other than the flake temperature are not particularly limited, and are appropriately selected depending on the amount of residual organic solvent required for the desired polycarbonate powder, productivity, etc. From the standpoint of obtaining the above, it is preferable to set the conditions for pulverization other than the flake temperature so that the proportion of the pulverized product having a particle size larger than 14 mesh in the pulverized product is 5% by weight or less. In this case, the setting of the conditions for pulverization other than the flake temperature is performed by appropriately selecting, for example, the power applied to the pulverizer and the pulverization time according to the performance of the pulverizer used.

The average particle size of the pulverized polycarbonate obtained by the method of the present invention is smaller than that obtained by the conventional method (14 mesh) when the crushing conditions other than the flake temperature are the same. Lower proportion of pulverized material with a larger particle size than. Further, the productivity (processing capacity of the crusher) at this time is higher in the method of the present invention than in the conventional method. Therefore, according to the present invention, it is possible to obtain a polycarbonate pulverized product which is easy to dry with high productivity. Further, since the average particle size of the obtained pulverized product is smaller than that obtained by the conventional method, the pulverized product is easier to handle than the conventional method. In the method of the present invention, the means for drying the pulverized product obtained as described above is not particularly limited, and various conventional methods applied when obtaining a polycarbonate powder can be applied as they are. The drying conditions at this time are appropriately selected according to the amount of residual organic solvent required for the desired polycarbonate powder, the productivity, etc., but for general grades, improvement of thermal stability and YI (Yell
ow Index: When the purpose is to improve the yellowness) or when manufacturing polycarbonate powder for special grade food products (low methylene chloride) or optical disk substrates, the residual organic solvent content should be 160 ppm or less. It is preferable to set conditions such as a drying temperature (crushed product temperature), a drying time, and an atmospheric pressure so as to achieve the above. When a polycarbonate crushed product having an organic solvent of methylene chloride and a particle size of 5% by weight or less having a particle size larger than 14 mesh is obtained,
Polycarbonate powder having a residual methylene chloride content of 200 ppm or less can be obtained by drying at 150 ° C. under normal pressure to reduced pressure for 5 minutes to 24 hours.

[0011]

Embodiments of the present invention will be described below. Example 1 First, a methylene chloride solution of polycarbonate was concentrated and powdered by a conventional method to obtain polycarbonate flakes.
Then, the polycarbonate flakes were pre-dried at 130 ° C. to obtain flakes having an amount of residual methylene chloride of 9.7% by weight. The ratio of flakes having a particle size larger than 14 mesh in the flakes after predrying was 45.2% by weight. Subsequently, the pre-dried flakes were cooled to 35 ° C. at a cooling rate of 2 ° C./sec by a horizontal powder cooler, and then an impact crusher M manufactured by Hosokawa Micron Co., Ltd.
Using VM-15 (trade name) with an internal volume of 50 liters, pulverization treatment was performed under the conditions of a flake temperature of 35 ° C., an atmospheric pressure of 300 mmH ₂ O, a pulverization medium rotation number of 5200 rpm, and a treatment time of 5 minutes to obtain a pulverized polycarbonate product. Obtained. The processing capacity of the crusher at this time was 31.5 kg / kW / hour. The ratio of the pulverized material having a particle size larger than 14 mesh in the obtained pulverized material was as low as 2.6% by weight. Thereafter, the obtained pulverized product was dried at 145 ° C. and a pressure (absolute pressure) of 720 mmHg for 5 hours to obtain a polycarbonate powder. The amount of residual methylene chloride in the obtained polycarbonate powder was 150 ppm, and the amount of residual organic solvent was small.

Example 2 Preliminarily dried flakes were obtained in the same manner as in Example 1, and the flakes were cooled to 45 ° C. under the same conditions as in Example 1,
Pulverized polycarbonate was obtained by pulverizing under the same conditions as in Example 1 except that the flake temperature was changed to 45 ° C. The processing capacity of the crusher at this time was 26 kg / kW / hour. The ratio of the pulverized material having a particle size larger than 14 mesh in the obtained pulverized material was as low as 2.5% by weight. Then, the obtained pulverized product was dried under the same conditions as in Example 1 to obtain a polycarbonate powder. The amount of residual methylene chloride in the obtained polycarbonate powder was 140 ppm, and the amount of residual organic solvent was small.

Example 3 Preliminarily dried flakes were obtained in the same manner as in Example 1, and the flakes were cooled to 55 ° C. under the same conditions as in Example 1,
Pulverized polycarbonate was obtained by pulverizing under the same conditions as in Example 1 except that the flake temperature was 55 ° C. The processing capacity of the crusher at this time was 23 kg / kW / hour. The ratio of the pulverized material having a particle size larger than 14 mesh in the obtained pulverized material was as low as 2.6% by weight. Then, the obtained pulverized product was dried under the same conditions as in Example 1 to obtain a polycarbonate powder. The amount of residual methylene chloride in the obtained polycarbonate powder was 155 ppm, and the amount of residual organic solvent was small.

Comparative Example 1 Preliminarily dried flakes were obtained in the same manner as in Example 1, and after cooling the flakes to 100 ° C. under the same conditions as in Example 1, the flake temperature was 100 ° C., which is outside the range of the present invention.
Except for the above, pulverization was performed under the same conditions as in Example 1 to obtain a pulverized product of polycarbonate. The proportion of the pulverized material having a particle size larger than 14 mesh in the obtained pulverized material was as low as 6.3% by weight, but the processing capacity of the pulverizer at this time was 13 kg / kW /
It was time, and the efficiency was low as compared with Examples 1 to 3. Then, the obtained pulverized product was dried under the same conditions as in Example 1 to obtain a polycarbonate powder. The amount of residual methylene chloride in the obtained polycarbonate powder was 330 ppm, and the amount of residual organic solvent was relatively large.

Comparative Example 2 Preliminarily dried flakes were obtained in the same manner as in Example 1, and after cooling the flakes to 75 ° C. under the same conditions as in Example 1,
A polycarbonate pulverized product was obtained by pulverizing under the same conditions as in Example 1 except that the flake temperature was set to 75 ° C., which is outside the range of the present invention, and the obtained pulverized product was dried under the same conditions as in Example 1 to give a polycarbonate. A powder was obtained. The proportion of the pulverized material having a particle size larger than 14 mesh in the pulverized material obtained under the above conditions was as low as 3.4% by weight, and the amount of residual methylene chloride in the finally obtained polycarbonate powder was 180.
It was relatively low as ppm. However, the processing capacity of the crusher when obtaining the crushed product was 18 kg / kW / hour, and the efficiency was lower than in Examples 1 to 3.

[0016]

As described above, according to the method of the present invention, a polycarbonate powder having a small amount of residual organic solvent can be produced from a solution of polycarbonate in an organic solvent with higher productivity than the conventional method. Therefore, according to the present invention, it is possible to provide a polycarbonate powder capable of improving the color tone and thermal stability of a product with high productivity.

Claims (3)

[Claims] 1. A method for producing a polycarbonate powder, which comprises obtaining a polycarbonate flake by concentrating and pulverizing a solution of a polycarbonate in an organic solvent to obtain a polycarbonate flake, preliminarily drying the pulverized pulverized product, and pulverizing the pulverized product to obtain a polycarbonate powder. In the method, the polycarbonate flakes after the preliminary drying are
A method for producing a polycarbonate powder, which comprises pulverizing at a flake temperature in the range of -60 ° C. 2. The pre-dried polycarbonate flakes are crushed at a flake temperature in the range of 10 to 60 ° C. to obtain a crushed product in which the proportion of flakes having a particle size larger than 14 mesh is 5% by weight or less. The method for producing the polycarbonate powder according to claim 1. 3. The crushed product is dried until the amount of residual organic solvent is 160 ppm or less.
The method for producing a polycarbonate powder according to item 1.