JP3183951B2 - Method for removing residual solvent from 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 removing good solvents and non-solvents remaining in polycarbonate powder. More specifically, the present invention relates to a method for efficiently removing a good solvent or a non-solvent from a polycarbonate powder having a good solvent or a non-solvent remaining to obtain a polycarbonate powder having a large bulk specific gravity.

[0002]

2. Description of the Related Art Polycarbonate is usually produced by a so-called solution method in which an aqueous alkali solution of a dihydric phenol and phosgene are reacted in the presence of an organic solvent. The organic solvent is removed from the resulting organic solvent solution of polycarbonate, and a drying step is carried out. It is obtained as a granular material through the process. A considerable amount of organic solvent remains in the powder, and it is difficult to sufficiently remove the residual organic solvent by ordinary drying.

As a method for producing polycarbonate powder having a small amount of residual organic solvent, a method of adding a non-solvent to an organic solvent solution of polycarbonate obtained by the reaction or a slurry of polycarbonate powder in which the organic solvent remains is proposed. Have been. However, the polycarbonate powder obtained by such a method is easily swollen or crystallized, and depending on the drying method, fine powder is generated at the time of drying, and the handleability is deteriorated. Further, in the polycarbonate powder obtained by the non-solvent treatment method, although the organic solvent used in the reaction is sufficiently removed, a large amount of non-solvent remains, and the residual non-solvent is sufficiently removed by ordinary drying. It is difficult.
If a large amount of non-solvent remains, vent up during extrusion molding,
Problems such as a decrease in work efficiency at the time of metallizing and a decrease in safety at the time of drying occur.

If the powder is made porous in order to increase the drying efficiency, the bulk specific gravity becomes small, and the handleability and the stability during molding are deteriorated. Further, if the porous powder is pulverized to further reduce the particle size in order to further increase the drying efficiency, all of the handling properties, hygiene due to dust generation, and the stability during molding will be deteriorated.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for efficiently removing a good solvent or a non-solvent from a polycarbonate powder in which a good solvent or a non-solvent remains to obtain a polycarbonate powder having a large bulk specific gravity. It is to provide.

The inventor of the present invention has conducted intensive studies to achieve the above object. As a result, a good solvent and a non-solvent were obtained by contacting a polycarbonate powder containing a good solvent and a non-solvent with a gas of a poor solvent followed by heat treatment. Have been found to be able to be removed efficiently, and the bulk specific gravity of the obtained polycarbonate powder is large, and the present invention has been completed.

[0007]

Means for Solving the Problems The present invention, as the good solvent
Methylene chloride and / or hexane or
Contacting acetone gas of a poor solvent of 5 parts by weight or more with 100 parts by weight of the polycarbonate powder particles in which heptane remains, and then heat-treating at a temperature not lower than the boiling point of the good solvent, non-solvent and poor solvent
Polycarbonate that is, and removing the residual solvent
This is a method for obtaining a granulated powder .

The polycarbonate referred to in the present invention is a polycarbonate obtained by reacting a dihydric phenol with a carbonate precursor. The dihydric phenol used here has the following general formula

[0009]

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Wherein R is a divalent aliphatic group having 1 to 15 carbon atoms, an alicyclic group, a phenyl-substituted aliphatic group, -O-, -S
—, —SO—, —SO ₂ — or —CO—, X is an alkyl group or a halogen atom, and m and n are 0, 1 or 2. In particular, 2,2-bis (4-hydroxyphenyl) propane [commonly known as bisphenol A] is preferably used. 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, bis (4-hydroxyphenyl) ether, etc.
Further, halogenated bisphenols such as 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane and the like can be mentioned. These may be used alone or in combination of two or more. Examples of the carbonate precursor include carbonyl halide, carbonyl ester, and haloformate, and specific examples include phosgene, diphenyl carbonate, and dihaloformate of dihydric phenol. Further, for example, a branched polycarbonate obtained by reacting a trifunctional or higher polyfunctional aromatic compound with a dihydric phenol and a carbonate precursor may be used, or a mixture of two or more polycarbonates may be used. The degree of polymerization of the polycarbonate does not need to be particularly limited, and is usually 13000 to 200,000 in terms of viscosity average molecular weight.

A typical example of a good solvent is methylene chloride , a typical example of a poor solvent is acetone , and a typical example of a non-solvent is hexane, heptane or the like. can give.

[0012] The above-mentioned polycarbonate powder or granules to be used in the present invention may be those produced by an arbitrary method, but are those in which a good solvent or a non-solvent remains. The amount of the residual good solvent and non-solvent need not be particularly limited, but is usually 0.0005% by weight or more, and preferably about 2.5% by weight or less. The water content of the polycarbonate powder is usually 1% by weight or less. Further, the shape of the polycarbonate powder is arbitrary, and the size thereof does not need to be limited as long as it is a size that is generally called a powder.

The amount of the poor solvent gas to be brought into contact with the polycarbonate powder is 5 parts by weight or more based on 100 parts by weight of the polycarbonate powder. If the amount does not reach 5 parts by weight, the good solvent and the non-solvent cannot be sufficiently removed. The amount of the poor solvent gas may be increased, but if it is 500 parts by weight or more, the effect of removing the solvent becomes saturated. The concentration of the poor solvent gas need not be particularly limited, and may be appropriately selected in consideration of safety, efficiency, and the like. Usually, it is used in the range of 50 to 100% by weight.

In order to bring the poor solvent gas into contact with the polycarbonate powder, any method may be employed as long as the poor solvent gas uniformly contacts the polycarbonate powder and does not condense the poor solvent gas. A method of supplying a poor solvent gas to the polycarbonate powder in a packed tower maintained at a temperature, the poor solvent gas while stirring the polycarbonate powder held at a temperature equal to or higher than the boiling point of the poor solvent by a paddle dryer, a Nauter mixer, or the like. Is preferable. The contact conditions such as the temperature of the poor solvent gas, the supply speed, the pressure of the contact atmosphere (reduced pressure, normal pressure, and pressurized) and the contact time need not be particularly limited, but the contact is preferably performed for 3 minutes or more, and preferably for 5 minutes or more. It is particularly preferred to make contact.

An arbitrary apparatus is used for the heat treatment performed after the contact with the poor solvent gas. For example, a fluidized drier, a paddle type drier, a hot air drier and the like can be mentioned, and an explosion-proof type is preferable. The treatment temperature is a temperature higher than the highest boiling point of the good solvent, the non-solvent, and the poor solvent, and is usually preferably about 120 to 150 ° C. Although the heat treatment time does not need to be particularly limited,
It is usually at least 20 minutes, preferably about 40 minutes to 8 hours.

[0016]

EXAMPLES Examples will be further described below with reference to examples. In addition,
Parts and% in the examples are parts by weight and% by weight,
For the determination of n-heptane and acetone, dioctyl sebacate was used as a column filler by gas chromatography [type 263, manufactured by Hitachi, Ltd.], and n-heptane was 2%.
The measurement was performed at 50 ° C. and acetone at 150 ° C. by the headspace method. The chlorine content was analyzed by a total organic halogen analyzer [TOX manufactured by Mitsubishi Kasei Corporation].

[0017]

Example 1 (A) A 15% methylene chloride solution of a polycarbonate having a viscosity average molecular weight of 23,500 obtained from bisphenol A and phosgene was put into a kneader to remove methylene chloride, coarsely pulverized, and then equipped with a screen having an aperture of 4 mm. After pulverizing by a hammer mill, water was added to obtain a slurry having a polycarbonate powder particle concentration of 25% and a liquid temperature of 35 ° C.

(B) 20 parts of n-heptane was added to 100 parts of polycarbonate and mixed with the slurry, dewatered by a centrifugal separator, and then dried at 145 ° C. for 2 hours by an explosion-proof hot-air circulating drier to obtain n-heptane. Heptane residual amount 10100
ppm and a residual amount of chlorine of 500 ppm were obtained.

(C) 100 parts of the polycarbonate powder was charged into a kneader equipped with a biaxial jacket having a vent port on the top and a gas inlet on the bottom, and the temperature was raised to 80 ° C. When the temperature reached 80 ° C., acetone gas having a concentration of 100% and a temperature of 80 ° C. was supplied from the gas inlet at a rate of 5 parts / minute, and simultaneously degassed from the vent. When the supply amount of the acetone gas reaches 300 parts, the supply of the acetone gas is stopped, and then the explosion-proof hot-air circulating dryer is used.
Heat treatment was performed at 5 ° C. for 8 hours. Table 1 shows the average particle size, bulk specific gravity, and residual solvent amount of the polycarbonate powder after the heat treatment.

[0020]

Example 2 The slurry A obtained in Example 1 (A) was dewatered by a centrifugal separator and dried at 140 ° C. for 8 hours by a fluidized drier to leave 0 ppm of n-heptane and 250 ppm of chlorine.
Was obtained.

100 parts of this polycarbonate powder is
The mixture was charged into the kneader equipped with a biaxial jacket used in Example 1, and when the temperature of the polycarbonate powder reached 80 ° C., acetone gas having a concentration of 100% and a temperature of 80 ° C. was supplied at 5 parts / min. At the same time as supplying at a speed, deaeration was performed from the vent. When the supply amount of the acetone gas reached 100 parts, the supply of the acetone gas was stopped, and then heat treatment was performed at 145 ° C. for 8 hours using an explosion-proof hot air circulation dryer. Table 1 shows the average particle size, bulk specific gravity, and residual solvent amount of the polycarbonate powder after the heat treatment.

[0022]

EXAMPLE 3 Residual amount of n-heptane obtained in Example 1 (B) 10
100 parts of a polycarbonate powder having 100 ppm of chlorine and a residual amount of chlorine of 500 ppm were charged into a jacketed packed tower having a vent port at the top and a gas inlet at the bottom, and the temperature was raised to reach a temperature of 80 ° C. At this time, acetone gas with a concentration of 100% and a temperature of 80 ° C.
At the rate of parts / minute and degas from the vent at the same time.
When the supply amount of acetone gas reached 20 parts, the supply of acetone gas was stopped, and then heat treatment was performed at 145 ° C. for 8 hours using an explosion-proof hot air circulation dryer. Table 1 shows the average particle size, bulk specific gravity, and residual solvent amount of the polycarbonate powder after the heat treatment.

[0023]

Comparative Example 1 Residual amount of n-heptane obtained in Example 1 (B) 10
A polycarbonate powder having 100 ppm and a chlorine residual amount of 500 ppm was dried at 145 ° C. for 8 hours by an explosion-proof hot air circulation dryer. Table 1 shows the average particle size, bulk specific gravity, and residual solvent amount of the dried polycarbonate powder.

[0024]

[Table 1]

[0025]

According to the present invention, a good solvent and a non-solvent can be efficiently removed from a polycarbonate powder in which a good solvent and a non-solvent remain by a very simple treatment. The body has a high bulk specific gravity and is easy to handle, and its industrial effect is outstanding.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshinori Kitachi 1-6-21 Nishishinbashi, Minato-ku, Tokyo Teijin Chemicals Co., Ltd. (56) References JP-A-54-101771 (JP, A) JP-A-61-55118 (JP, A) JP-A-5-78494 (JP, A) JP-A-5-17579 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 64 / 00-64/42

Claims (1)

(57) [Claims] 1. A poor solvent of 5 parts by weight or more per 100 parts by weight of a polycarbonate powder containing methylene chloride as a good solvent and / or hexane or heptane as a non- solvent.
How good solvent after contacting the acetone gas, heat-treated at a temperature higher than the boiling point of the non-solvent and a poor solvent, to obtain a polycarbonate powder and granular material, characterized in the this <br/> to remove residual solvent.