JPH0762074B2 - 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 from a solution of polycarbonate in an organic solvent, and more specifically,
It relates to a method for producing polycarbonate granules which do not exhibit a melting point.

<Prior Art> Many methods for producing polycarbonate granules from a solution of polycarbonate in an organic solvent have already been proposed.
That is, the hot water region is brought into contact with water vapor to form flakes or granules, concentrated, cooled or gelled by adding polycarbonate powder and then pulverized, or a non-solvent or poor solvent is added for gelation. Known is a method of pulverizing or granulating.

Polycarbonate A generally derived from bisphenol A is polyethylene terephthalate or nylon 6.6.
Unlike, it is considered to be a polymer that is difficult to crystallize. However, when it contains an organic solvent, particularly under the condition that a shearing force acts, it tends to crystallize,
Many of the polycarbonate granules obtained by the above method show a clear melting point in DSC measurement.

In the prior art, Japanese Examined Patent Publication No. 40-3533 discloses 40 to 10
It is disclosed that the flakes obtained by pouring a solution of polycarbonate into turbulent water at 0 ° C, especially 90 to 100 ° C, are hardly crystallized, but the flakes obtained by this technique contain many Since it has a space of, the bulk density is 0.1 g / cm ³ or less, which is extremely inconvenient in handling. As a means for avoiding the formation of flakes or increasing the bulk density, Japanese Patent Publication No. 46-37424 discloses stirring.
Disclosed is a method of injecting a polycarbonate solution through pores above or below the surface of warm water of ~ 75 ° C.
The solid polycarbonate obtained is in the form of small balloons (JP-A-59)
However, it is difficult to obtain a satisfactory granular material suitable for molding. Further, as an improved method, JP-A-59-133228 and JP-A-61-27208 propose a method of circulating a part of the water slurry in the granulation tank through a wet pulverizer. The apparatus becomes complicated, and piping clogging occurs between the granulation tank and the crusher, or crystallization occurs in the crushing process, which is not always satisfactory.

<Object of the Invention> An object of the present invention is to provide a method for obtaining amorphous polycarbonate granules which do not show a melting point in DSC measurement from an organic solvent solution of polycarbonate using a simple apparatus.

<Structure of the Invention> The present invention is a polycarbonate granule produced by continuously supplying an organic solvent solution of polycarbonate while stirring a mixture of a polycarbonate granule containing a small amount of an organic solvent and warm water, and evaporating the solvent. In the method of continuously discharging the body out of the system, the temperature of the hot water exceeds 60 ° C,
And maintained within the range of 80 ° C. or less, and maintaining the amount of the polycarbonate particles in the system within the range of 25 to 40% by weight based on the total weight of the polycarbonate particles and the warm water. It is a manufacturing method of a granular body.

The polycarbonate used in the present invention is polycarbonate A derived from bisphenol A, but with a small proportion of other dihydric 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-)
A copolymer of hydroxyphenyl) sulfone and a nucleus lower alkyl-substituted product thereof, in which about 26% by weight or more of a methylene chloride solution gels at room temperature, is also used. Further, as the organic solvent, methylene chloride, ethylene dichloride, chloroform and the like can be preferably used a lower chlorinated hydrocarbon having a boiling point of about 60 ° C or higher.

The organic solvent solution of polycarbonate may be prepared by dissolving polycarbonate in an organic solvent, but an organic solvent solution of polycarbonate obtained by reacting a dihydric phenol with phosgene in the presence of an organic solvent is preferably used. The concentration of polycarbonate in the solution is usually about 10 to about
20% by weight.

The granulating tank used in the practice of the present invention may be any one as long as the contents can be sufficiently stirred and mixed, and for example, a kneader can be preferably used.

In the present invention, a polycarbonate organic solvent solution in a stirring state is continuously supplied to continuously evaporate the solvent while continuously discharging the produced polycarbonate particles. It is a requirement that the hot water in the granulation tank is maintained above 60 ° C and below 80 ° C. When the temperature is 60 ° C or lower, the evaporation rate of the solvent becomes slow, and the concentration of the polycarbonate in the supplied organic solvent solution of the polycarbonate gradually increases. It is said that the concentration suitable for crystallization of the polycarbonate is 26 to 60% by weight. It is not suitable because the time in the range of% becomes long and crystallization occurs. Further, when the temperature exceeds 80 ° C, the supplied organic solvent solution of the polycarbonate is solidified by containing voids inside, and the flakes (granular particles) are shaped like small balloons or become tempura-like, which is not suitable. The temperature is maintained by supplying hot water or steam, jacket heating, etc., but it is necessary to take care not to locally heat the contents especially when steam is supplied.

Further, the supply port for supplying the organic solvent solution of the polycarbonate to the granulation tank, it is desirable that the continuously discharged solution is discharged from the entire surface of the supply port, but it is not possible to make it small, for example, 1 mm or less Not necessarily required. The position of the supply port is preferably the upper space in the granulation tank, and the position where the discharged solution is dispersed in the mixture of the polycarbonate granules and warm water as quickly as possible.

Further, the amount of the polycarbonate granules in the granulation tank is 25 based on the total weight of the polycarbonate granules and the warm water.
It is necessary to maintain within the range of -40% by weight. The supplied organic solvent solution of polycarbonate rapidly increases in viscosity while being heated by warm water and granules to evaporate the solvent and changes into a solid, but in the process, it adheres to the granules, which becomes granular. It is torn off and subdivided by the light friction of the same body. Therefore, if the amount of the polycarbonate granules is less than 25% by weight, the friction between the granules is hindered by the water layer interposed therebetween.
Polycarbonate adhered to the surface of the granules is not torn off and solidifies as it is to form a porous mass,
On the other hand, small balloon-shaped flakes are produced from the polycarbonate solution which has not adhered to the granules.

On the other hand, when it exceeds 40% by weight, the stirring and mixing of the polycarbonate granules and hot water become non-uniform, resulting in uneven temperature and excessive friction between the granules, resulting in a large distribution of the granules. The result will be spread to. Thus, a more preferred amount range of polycarbonate granules is greater than 30% and less than or equal to 40% by weight.

The generated polycarbonate granules and excess warm water are
It becomes a slurry and is continuously discharged from below the surface of the mixture in the tank. If necessary, the temperature of the discharged slurry is further raised by vapor suction to remove the organic solvent contained in the polycarbonate granules, and then the polycarbonate granules are recovered by filtration, centrifugation or the like and dried.

When the polycarbonate granules obtained by the method of the present invention are used for optical applications, the granules are dissolved in an organic solvent and the amount of foreign fine particles mixed therein is measured by an automatic fine particle measuring instrument. The smaller the amount of foreign particles, the better. In the present invention, the foreign particle is mainly a component of the material forming the granulation tank, and the mixing ratio thereof largely depends on the stirring power of the granulation tank. Therefore, the ratio of the polycarbonate granules in the granulation tank exceeds, for example, 30% by weight,
It is desirable to keep the amount in the range of 35% by weight or less and to quickly discharge the produced slurry.

Further, in order to suppress the generation of the foreign particles, austenitic stainless steel, Fe-Cr-
It is preferable to use an alloy having a Ni content of 11% by weight or more, such as a Ni alloy, a Ni-Cr-Fe alloy, or a Ni-Mo-Fe-Cr alloy.

<Effects of the Invention> Since the polycarbonate granules obtained by the present invention are porous, dehydration and desolvation by a known method are easy. The dry granules thus obtained have a bulk density of about 0.3 to about 0.
6, grain size of about 0.1 to about 10 mm, but the most significant feature is a low melting point or no melting point, that is, not crystallized or low crystallinity. Polycarbonate A granules obtained by the conventionally known gelling method have a temperature of about 235 ° C to 250 ° C.
Since it has a melting point of, it was necessary to set the resin temperature to at least about 240 ° C. or higher during melt molding. However, since the polycarbonate of the present invention can be melted at a low temperature, in the melt blending with a styrene resin, an acrylic resin or the like, it is possible to avoid the disadvantages such as depolymerization of these resins.

Further, conventional polycarbonates having a melting point do not have a kneading function in powder molding such as rotational molding, and thus it is necessary to further raise the temperature. However, since the polycarbonate granules according to the present invention are not crystallized, it is possible to lower the resin temperature during molding by at least about 10 ° C. In this way, depolymerization during melt blending can be significantly reduced, and electric power, fuel, etc. in melt molding can be saved, and industrially excellent effects can be brought about.

<Example> The present invention will be described in detail below with reference to Examples.

Example 1 A kneader with an internal capacity of 500 equipped with a solution supply port, a steam inlet, a hot water inlet, a steam outlet and an overflow port had a bulk density of about
100g of 0.5g / cc amorphous polycarbonate powder and warm water
200 Kg was added and stirred. When the water temperature reached approximately 65 ° C, continuously supply a methylene chloride solution with a polycarbonate concentration of 15% by weight at a rate of 10 Kg / min while continuing stirring, and at the same time generate steam with a pressure of 2.7 Kg / cm ² . Introduction of hot water at 65 ° C. at a rate of 1.26 Kg / min and 2.37 Kg / min was started. The water temperature was maintained at about 65 ° C, and a water slurry having a polycarbonate concentration of about 33% by weight was continuously discharged from the overflow port. Further, the evaporated methylene chloride was introduced from the outlet to the condenser and separated from the accompanying water. The polycarbonate powder and granules were separated from the discharged water slurry by centrifugation and dried. The bulk density was 0.51 g / cc and no melting point was shown by DSC measurement.

Example 2 The same operation as in Example 1 was carried out except that the water temperature was about 75 ° C., the steam speed was 1.31 Kg / min, and the hot water speed was 2.91 Kg / min. The bulk density of the obtained polycarbonate powder is 0.41 g /
Melting point was not found by DSC measurement with cc.

Comparative Example 1 The same operation as in Example 1 was carried out except that the water temperature was about 55 ° C., the steam rate was 1.22 Kg / min, and the hot water speed was 2.10 Kg / min.
The bulk density of the obtained polycarbonate powder is 0.63 g / cc.
DSC measurement showed a melting point of 234 ° C.

Claims (1)

[Claims] 1. A polycarbonate granule produced by continuously feeding a solution of a polycarbonate organic solvent in a stirring state to a mixture of a polycarbonate granule containing a small amount of an organic solvent and warm water to evaporate the solvent to continuously produce a polycarbonate granule. In the method of discharging the hot water to the outside of the system, the temperature of the hot water is maintained in the range of more than 60 ° C. and 80 ° C. or less, and the amount of the polycarbonate particles in the system is the total weight of the polycarbonate particles and the hot water. A method for producing polycarbonate granules, characterized in that the content of the polycarbonate granules is maintained in the range of 25 to 40% by weight.