JPH0816165B2 - Method for producing polycarbonate granular material - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing polycarbonate granules. More particularly, it relates to a method for economically producing a polycarbonate granule having a high bulk specific gravity, an appropriate particle diameter, excellent handleability, and an extremely small amount of residual solvent from a solution of a polycarbonate in an organic solvent.

[0002]

2. Description of the Related Art Conventionally, as a method for obtaining a polycarbonate granule by removing a solvent from an organic solvent solution of polycarbonate, as described in JP-B-45-9875, a gel is formed in warm water. The method of pulverizing afterwards is common. However, the granules produced by this method have a high bulk specific gravity of 0.6 to 0.65 and are easy to handle, but have poor dryability because they have undergone a crystallization process, and the amount of residual solvent in the granules is high. In order to reduce the above, the particle size cannot be increased, and there are drawbacks such that a defective biting is likely to occur when melt molding is performed using the obtained granular material.

Therefore, as proposed in Japanese Patent Laid-Open No. 60-54329 and Japanese Patent Publication No. 46-3724,
There has been proposed a method of improving dryness by granulating in high temperature water to make it porous. However, according to such a method, the obtained granular material has a bulk specific gravity of 0.3 to 0.4.
However, there is a drawback in that the handleability is poor.

On the other hand, various methods of granulating using a non-solvent for polycarbonate have been proposed. For example, in JP-B-46-31468, a method using toluene is disclosed in JP-B-55-21773 and JP-A-64-31.
A method using heptane is proposed in Japanese Patent No. 690. The granules obtained by these methods have a bulk specific gravity of 0.4 to
When it is 0.5, it is porous and has good dryness, which is an excellent method. However, since the non-solvent is added to the polycarbonate solution and mixed, the non-solvent is mixed in the solvent recovered in the granulation step, and there is a drawback that the rectification and removal of the non-solvent causes a significant increase in cost. Without using it as a polymerization solvent as it is, it is necessary to use explosion-proof equipment up to the polymerization equipment and the like, and there is a drawback that a large amount of capital investment is required.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a method for economically producing a polycarbonate granule having a high bulk specific gravity, an appropriate particle diameter, excellent handleability, and a small amount of residual solvent. To aim. Originally, the bulk specific gravity and the particle size had a negative correlation with the drying property, and the handling properties of the polycarbonate granules and the amount of residual solvent were not compatible, and various restrictions were imposed during the granulation process. The object of the present invention is to break the negative relationship between the particle size and the drying property.

[0006] As a result of earnest studies by the inventor of the present invention, the organic solvent solution of polycarbonate is heated in warm water to remove the solvent, and the resulting aqueous slurry of the granular material contains the non-polycarbonate. Add solvent and mix,
After that, if the polycarbonate granules are separated and dried,
Bulk specific gravity is high, particle size is uniform, handling is excellent, and it is easy to obtain a polycarbonate granule with a small amount of residual solvent,
In addition, it was found that the amount of the non-solvent used and the amount of the solvent mixed with the non-solvent can be remarkably reduced as compared with the conventional method using the non-solvent, which is extremely economical.

In this method, the conventional method using a non-solvent is a method in which a non-solvent is added to a polycarbonate solution and then granulated, but in the water slurry obtained after granulation is completed. A non-solvent is added. Since non-solvents have extremely weak penetrating power to polycarbonate,
When added in a water slurry state, it was thought that the non-solvent did not penetrate into the polycarbonate granules, but a considerable amount of solvent remained in the polycarbonate of the water slurry, and the solvent and non-solvent were compatible. It was found that the non-solvent sufficiently penetrates into the polycarbonate granules due to its properties, and thus completed the present invention.

[0008]

Means for Solving the Problems In producing a polycarbonate granular material from an organic solvent solution of polycarbonate, the present invention heats the polycarbonate organic solvent solution in warm water to remove the organic solvent and granulate the polycarbonate. After that, the polycarbonate granules are taken out as a water slurry, and a non-solvent of polycarbonate or a mixed solution of the non-solvent and an organic solvent is added to the slurry in an amount such that the amount of the non-solvent becomes a polycarbonate weight ratio of 0.001 to 1.0. Then, it is followed by separation and drying, which is a method for producing a polycarbonate granular material.

The polycarbonate referred to in the present invention is a polycarbonate obtained by reacting an alkaline aqueous solution of a dihydric phenol with phosgene and a polyester carbonate obtained by copolymerizing a dicarboxylic acid component with the polycarbonate, and at least the polymerization is carried out in the presence of an organic solvent. The target is an organic solvent solution obtained by the reaction below. Further, in producing the polycarbonate, an appropriate catalyst or molecular weight modifier can be used.

As the dihydric phenol used here,
The main target is 2,2-bis (4-hydroxyphenyl) propane [commonly called bisphenol A], but part or all of it may be replaced with another dihydric phenol. Examples of the other dihydric phenol include bis (4-hydroxyphenyl) methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis ( 4-hydroxyphenyl)
Cyclohexane, 1-phenyl-1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) octane, bis (4-hydroxydiphenyl) ether, bis (4-hydroxyphenyl) ketone, Examples thereof include bis (4-hydroxyphenyl) sulfone, hydroquinone, resorcin, 4,4′-dihydroxydiphenyl, 2,6-dihydroxynaphthalene, and lower alkyl or halogen-substituted products thereof. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like.

As the alkali used in the alkaline aqueous solution of dihydric phenol, strong basic hydroxides such as caustic soda and caustic potash are preferred. These basic hydroxides are usually used as an aqueous solution, and the concentration thereof is usually 5 to 10% by weight. Further, the amount of the basic hydroxide used is preferably an amount that is slightly in excess of the theoretical amount of 2 times the molar amount of the dihydric phenol, and is preferably 2.2 to 3 times the molar amount of the dihydric phenol.

As the organic solvent, for example, tetrachloroethane, methylene chloride, 1,2-dichloroethane, chloroform, 1,1,2-trichloroethane, etc. are used.
These are used alone or as a mixture. Of these, methylene chloride is preferable, and methylene chloride is particularly preferable. However, it may contain halogenated hydrocarbon such as chloroform or dichloroethane, or may be recovered from the polymerization reaction of polycarbonate.

The polymer concentration in the organic solvent solution of polycarbonate, which is the object of the present invention, varies depending on the kind of the organic solvent, but in the case of a methylene chloride solution, the polymer concentration is 5
˜35% by weight is preferable, and 10 to 25% by weight is particularly preferable.

Any method may be employed in the granulating step of granulating the polycarbonate by heating the polycarbonate organic solvent solution in the present invention in warm water to remove the organic solvent. For example, a method of continuously supplying a polycarbonate organic solvent solution and warm water into a hot water slurry of polycarbonate granules in a stirring state, and continuously discharging the polycarbonate granules produced while evaporating the solvent as a water slurry, a granulating tank A preferred method is a so-called batch-type granulation method in which the polycarbonate organic solvent solution and steam are put in warm water, the organic solvent is removed to form a waxy gel, which is then crushed, and then discharged as a water slurry. Is. If the temperature in the granulation tank is too low, the granulation speed will decrease remarkably, and if it is too high, not only will there be a large amount of water vapor loss, but the interior of the granule will become extremely porous and the bulk specific gravity will decrease significantly. So 40-80 ° C
Is preferable, and 40 to 60 ° C. is particularly preferable. The granulating tank used here should just be able to stir and mix the contents, and for example, a kneader is preferable.

In the present invention, the polycarbonate non-solvent, which is discharged from the granulation tank, is added with the non-solvent of polycarbonate alone or in a mixture with the organic solvent. The non-solvent of the polycarbonate used here is substantially insoluble in water and soluble in the solvent used for the polycarbonate solution, and has a boiling point of 40 to 100 ° C. Examples of such a non-solvent include hydrocarbons such as hexane and heptane, alicyclic compounds such as cyclohexane and cyclohexanone, esters such as ethyl acetate and butyl acetate, and heptane is particularly preferable. A mixed solution of two or more non-solvents or a mixed solution of non-solvents and methylene chloride may be used. The boiling point of the solvent may be 100 ° C or higher, but the azeotropic point with water may be 100 ° C or lower.

The addition amount of the non-solvent depends on the kind of the solvent,
Generally, the weight ratio of the polymer is 0.001 to 1.0, preferably about 0.01 to 0.5. This amount is remarkably small as compared with the conventional method using a non-solvent. Any method can be adopted as a method of adding the non-solvent. It may be added continuously or batchwise to the water slurry of the polycarbonate granules that are uniformly stirred in a tank having a stirring mechanism.

When the non-solvent is added, the solvent remains in the polycarbonate particles of the water slurry, and the added non-solvent easily penetrates into the polycarbonate particles, but the residual solvent in the polycarbonate particles remains. If the amount is too small, the permeation amount of the non-solvent will be insufficient, and the amount of residual solvent in the obtained granular material will increase, or the permeation will take a long time. Further, if the residual solvent amount is too large, the amount of the solvent mixed with the non-solvent becomes large, which does not meet the purpose of the present invention. Therefore, the residual solvent concentration is set to 1% by weight or more based on the total weight of the polycarbonate and the organic solvent. It is preferable that the amount is 10 to 50% by weight. Further, the non-solvent may be added alone, but it is effective to add it as a mixed solution with an organic solvent.
When the non-solvent is added as a mixed solution with the organic solvent, even if the amount of the residual solvent in the polycarbonate granules is small, the permeation force of the organic solvent has the effect of enhancing the permeation of the non-solvent. The total amount of the organic solvent added together with the residual organic solvent and the non-solvent in the polycarbonate granules is preferably in the range of 5 to 70% by weight, particularly 10 to 50% by weight, based on the total weight of the polycarbonate and the organic solvent. It is preferable to be in the range.

The contact time between the polycarbonate granules and the non-solvent is most important for the stirring time after the addition of the non-solvent, but since the penetration of the non-solvent into the polycarbonate granules is extremely fast, the residence time of the polycarbonate granules in the tank is very high. Takes less than two hours and is almost complete in less than an hour. The optimum stirring time depends on the type and amount of the solvent and the particle size of the granules, but can be easily determined by experiments or the like.

In order to obtain the polycarbonate granules from the water slurry thus obtained, the solvent and non-solvent are distilled off from the water slurry and recovered, and then the granules are separated by means such as tilting, filtration and centrifugation. Then dry it. Since the recovered non-solvent still contains a large amount of solvent, it may be rectified and separated by an ordinary distillation method and reused. This recovery is remarkably economical because it requires a treatment amount of 1/10 to 1/50 as compared with the recovery of the non-solvent and solvent in the conventional method of adding a non-solvent to a polycarbonate solution for granulation.

According to the method of the present invention, the relationship between the particle size and the drying property can be cut off, only the particle size control needs to be taken into consideration in the granulation step, and if necessary, a wet pulverizer is added to the granulation tank. You may.

[0021]

EXAMPLES The present invention will be further described with reference to the following examples.

[0022]

[Reference example] A methylene chloride solution (concentration: 15% by weight) of a polycarbonate having a viscosity average molecular weight of 25,000, which was synthesized by a conventional method from bisphenol A and phosgene and purified.
In a kneader with a solution supply port, a steam inlet, a hot water inlet, a steam outlet, and an overflow port with an internal capacity of 50 liters, and 10 kg of polycarbonate granules having a bulk density of 0.62 g / cc.
And 20 kg of warm water are added and stirred, and when the water temperature reaches 41 ° C, the mixture is continuously supplied at a rate of 25.6 liters / hr while continuing stirring, and at the same time steam at a pressure of 2.7 kg / cm ² and 41 ° C. The introduction of the hot water of 4 kg / hr was started at a rate of 5 kg / hr. The water temperature was maintained at 41 ° C., and a water slurry having a polycarbonate concentration of about 33% by weight was continuously discharged, and at the same time, evaporated methylene chloride was introduced from a discharge port to a condenser and separated from water entrained. The residual methylene chloride content in the polycarbonate granules of the water slurry was 40% by weight.

[0023]

Example 1 50 kg of the polycarbonate water slurry obtained in Reference Example was placed in a 200-liter mixing tank having a stirring mechanism, and further 8.5 kg of heptane was placed therein and uniformly mixed for 30 minutes. During this time, the temperature in the tank is not particularly heated, 30-40 ° C
Maintained at. Then, steam having a pressure of 2.7 kg / cm ² was introduced into the same tank, the temperature was raised to 95 ° C., and the mixture was stirred for 30 minutes, and 8.0 kg of heptane and 11 kg of methylene chloride were distilled off. The polycarbonate aqueous slurry thus obtained was taken out, filtered with a centrifugal dehydrator, and dried at 140 ° C. for 4 hours with an explosion-proof hot air dryer. The obtained polycarbonate granules had an average particle diameter of 2.0 mm, a bulk specific gravity of 0.62 and a residual methylene chloride content of 10 ppm.

[0024]

[Example 2] The water slurry of the polycarbonate obtained in Reference Example was kept at 60 ° C for 30 minutes so that the residual methylene chloride content in the polycarbonate granules of the water slurry was 10% by weight. Polycarbonate granules were obtained in the same manner as in 1. The obtained polycarbonate granules had the same average particle diameter and bulk specific gravity as in Example 1, and the residual methylene chloride content was 8 ppm.

[0025]

Example 3 Cyclohexane was used instead of heptane in 8.5.
Polycarbonate granules were obtained in the same manner as in Example 1 except that kg was used. The obtained polycarbonate granules had the same average particle size and bulk specific gravity as in Example 1, and the residual methylene chloride content was 15 ppm.

[0026]

Example 4 Polycarbonate granules were obtained in the same manner as in Example 1 except that a mixed solution of 0.17 kg of heptane and 0.2 kg of methylene chloride was used instead of heptane. The obtained polycarbonate particles had the same average particle size and bulk specific gravity as in Example 1, and the residual methylene chloride content was 5 ppm.

[0027]

Example 5 The water slurry of the polycarbonate obtained in Reference Example was stirred at 90 ° C. for 1 hour to make the residual methylene chloride content in the polycarbonate particles of the water slurry 1% by weight, and 0.85 kg of heptane was added to this water slurry. Methylene chloride 3.
Polycarbonate granules were obtained in the same manner as in Example 1 except that 4 kg of the mixed solution was added. The obtained polycarbonate granules had the same average particle diameter and bulk specific gravity as in Example 1, and the residual methylene chloride content was 15 ppm.

[0028]

Comparative Example 1 Polycarbonate granules were obtained in the same manner as in Example 1 without adding heptane to the aqueous polycarbonate slurry obtained in Reference Example. The obtained polycarbonate granules had the same average particle diameter and bulk specific gravity as in Example 1, but
The amount of residual methylene chloride was extremely high at 2000 ppm.

[0029]

In the method for producing a polycarbonate granular material of the present invention, since a non-solvent is not mixed in the granulation step, a large amount of methylene chloride recovered in the granulation step can be reused as it is, and the non-solvent is added. Is a water slurry obtained in the granulation process, so the amount of non-solvent used is extremely small,
Its recovery cost is low, and its location is limited, so it is safe.

Therefore, according to the present invention, it becomes possible to economically and safely produce a polycarbonate granular material having a high bulk specific gravity, an appropriate particle diameter, excellent handleability, and an extremely small amount of residual solvent. The industrial effect produced by this is extremely large.

Claims (2)

[Claims] 1. When producing polycarbonate granules from an organic solvent solution of polycarbonate, the polycarbonate organic solvent solution is heated in warm water to remove the organic solvent to granulate the polycarbonate, and then the polycarbonate granules are treated with water. It is taken out as a slurry, and a non-solvent of polycarbonate or a mixed solution of the non-solvent and an organic solvent is added to the slurry, and the amount of the non-solvent is 0.001 by weight of the polycarbonate.
A method for producing a polycarbonate granule, which comprises adding and mixing in an amount of about 1.0, and then separating and drying. 2. The total amount of the organic solvent to be added together with the residual organic solvent and the non-solvent in the polycarbonate granules of the water slurry when the non-solvent is added is 5 to 70% by weight based on the total weight of the polycarbonate and the organic solvent. %. The method for producing a polycarbonate granular material according to claim 1, which is%.