JPH08281646A - Drying method for poloycarbonate granule - Google Patents

Abstract

PURPOSE: To dry polycarbonate granules at low costs by removing an organic solvent without changing particle size distribution and bulk density by setting a primary drying process in which the polymer granules containing the solvent is dried until the solvent content reaches a specified wt.% by adjusting a drying speed calculated by an equation at a specified value. CONSTITUTION: In a drying method for polycarbonate granules, the granules containing an organic solvent of 30-60wt.% are dried until the solvent content reaches 30wt.%. by adjusting a drying speed calculated by an equation to be 0.01[log(wt.%)/min] or less in a primary drying process. In the equation, t1 , t2 are measuring points, t2 >t1 , and Ca1 , Ca2 indicate the solvent contents (wt.%) of the granules at t1 , t2 . In this way, the generation of fine powder by the breakage of the polycarbonate granules is controlled to give similar particle size distribution and bulk density to those before drying, obtaining dried polycarbonate granules with a reduced organic solvent content.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drying a polycarbonate powder or granular material, and more particularly to removing a solvent contained in the polycarbonate powder or granular material without changing the particle size distribution or bulk density of the polycarbonate powder or granular material. The present invention relates to a method for drying a polycarbonate powder or granule.

[0002]

2. Description of the Related Art As a method for producing a polycarbonate, an interfacial polycondensation method using an aromatic dihydroxy compound such as bisphenol A and phosgene as raw materials is known. This interfacial polycondensation method
A polycarbonate is obtained by bringing an alkaline aqueous solution of an aromatic dihydroxy compound and phosgene into contact with each other in the presence of an organic solvent such as methylene chloride to carry out a polycondensation reaction at an interface between an aqueous phase and a solvent phase. According to this interfacial polymerization method, the polycarbonate is obtained in a solution state in which it is dissolved in an organic solvent. Therefore, in order to obtain the polycarbonate granules, it is necessary to remove the organic solvent by treatment such as concentration and drying.

The following methods are known as methods for obtaining polycarbonate powder particles from a polycarbonate solution.

(A) A method of evaporating and concentrating and drying a polycarbonate solution by supplying the polycarbonate solution to a stirring device such as a kneader and stirring the polycarbonate solution while heating (Japanese Patent Publication No. 53-15899). b) A method in which a polycarbonate solution is poured into warm water to precipitate a polycarbonate solid matter under stirring, and the precipitated polycarbonate solid matter is collected by filtration (JP-A-64-74231).
(C) A method of rapidly mixing a polycarbonate solution with steam to obtain a dispersion liquid of polycarbonate particles, and then removing water and a solvent by heating (JP-B-63-13).
No. 33) (d) A method of supplying a polycarbonate solution together with a polycarbonate seed powder and a poor solvent or a gas thereof to a granulation tank with a helical stirring blade, and heating while stirring and mixing to evaporate and remove the organic solvent and the poor solvent ( JP-A-6-100
However, a considerable amount of solvent generally remains in the polycarbonate powder particles obtained by the above methods (a) to (d), and such solvent-remaining polycarbonate powder particles are biaxially extruded. When it is dried with a blade dryer such as a dryer or paddle dryer, a large amount of fine powder is generated due to the breakage of powder and granules, and operational troubles such as clogging and accumulation of pipes occur. In addition, the generation of fine powder broadens the particle size distribution of the powder and granules, and the bulk density also greatly changes, which deteriorates the extrudability and handleability during polycarbonate molding.

In order to eliminate the above-mentioned drawbacks caused by the fine powder generated when drying the polycarbonate powder, the dried powder is classified to remove the fine powder, or only the removed fine powder is compression molded. There is a method, but this method is troublesome and leads to an increase in product cost.

Further, in Japanese Patent Laid-Open No. 6-155466,
A method is disclosed in which a polycarbonate powder is dried in a non-blade dryer until the residual amount of solvent is less than 5% by weight.

However, in the method described in this patent publication, it is necessary to use a special non-blade dryer which does not apply a shearing force to the powder or granules during drying, which increases equipment cost, which leads to an increase in product cost. . The method described in this patent publication, even if using a non-blade dryer,
When the drying speed is high, the generation of fine powder is unavoidable, and there are drawbacks that the above-mentioned troubles occur and extrudability and handleability deteriorate.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and the object thereof is to use any dryer, including a conventionally used blade dryer, to obtain a polycarbonate powder granule. An object of the present invention is to provide a method capable of drying a polycarbonate powder or granular material at low cost by removing the solvent contained in the polycarbonate powder or granular material without changing the particle size distribution or bulk density of the polycarbonate powder or granular material.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, until the solvent content of the polycarbonate powder is at least 30% by weight, the drying rate is set as follows. When dried to a predetermined value or less as shown, the generation of fine powder due to the destruction of the polycarbonate powder is suppressed even when using any dryer including a blade dryer, and as a result, the particle size distribution, It has been found that the polycarbonate granules can be dried without changing the bulk density.

The present invention has been completed based on the above findings, and a method for drying a polycarbonate powder according to the present invention comprises a polycarbonate powder containing an organic solvent in an amount of more than 30% by weight and 60% by weight or less, Solvent content is at least 3
The drying rate calculated by the following formula was adjusted to 0.
The method is characterized by including a primary drying step of drying at a rate of 01 [log (wt%) / min] or less.

Drying rate (Rd) = (log Ca ₁ -log C
a ₂ ) / (t ₂ −t ₁ ) t ₁ , t ₂ : indicates the measurement time point, and t ₂ > t ₁ . Ca _1, Ca _2: shows solvent content of the polycarbonate powder or granular material at time t _1, t ₂ (% by weight).

The present invention will be described in detail below.

In the present invention, the polycarbonate powder to be subjected to the drying treatment may be the one obtained by evaporating, concentrating and drying an organic solvent solution of polycarbonate by any method.

Typical examples of the above-mentioned "polycarbonate" include polycarbonate (A) obtained by the reaction of a dihydroxy compound and phosgene or the reaction of a dihydroxy compound and a carbonic acid ester, and a dihydroxy compound, phosgene and a dibasic carboxylic acid. The polyester carbonate (B) obtained by the reaction with

The dihydroxy compound which is a raw material for producing the above polycarbonate (A) and polyester carbonate (B) is preferably a dihydric phenol compound, and specific examples thereof include hydroquinone and 4,4'-.
Dihydroxydiphenyl, bis (4-hydroxyphenyl) alkane [bisphenol A, etc.], bis (4-hydroxyphenyl) cycloalkane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxy) Examples thereof include phenyl) sulfone, bis (4-hydroxyphenyl) ketone, and halogen-substituted compounds thereof. Examples of the carbonic acid ester compound that is a raw material for producing the polycarbonate (A) include diaryl carbonate such as diphenyl carbonate and dialkyl carbonate such as dimethyl carbonate and diethyl carbonate.

The above polyester carbonate (B)
Examples of the dibasic carboxylic acid, which is a raw material for producing, include terephthalic acid and isophthalic acid.

The "organic solvent" in the above "organic solvent solution of polycarbonate" is (a) dissolving the polycarbonate, (b) substantially inert to the polycarbonate, (c) substantially at the use temperature. As long as it satisfies the condition that it is physically stable, its kind does not matter. However, considering removal from the polycarbonate powder, an organic solvent having a boiling point of 200 ° C. or lower is desirable.

Specific examples of such an organic solvent include methylene chloride, which is usually used preferably, and chlorine-based organic solvents such as chloroform and chlorobenzene.
Examples include solvents such as dioxane and tetrahydrofuran, or a mixture thereof. The organic solvent may be a mixture with a poor solvent. The poor solvent does not substantially dissolve the polycarbonate and is stable at the temperature of use, and specific examples thereof include aliphatic alkanes, aromatic alkanes, alcohols, ketones and the like.

The method for obtaining a polycarbonate powder from an organic solvent solution of polycarbonate is not particularly limited as long as it is a method capable of obtaining a polycarbonate powder containing an organic solvent in an amount of more than 30% by weight and 60% by weight or less. It is not something that will be done. For example, the following method may be mentioned.

(I) A method in which a polycarbonate solution is supplied to a stirring device such as a kneader, and the polycarbonate solution is stirred while being heated to evaporate and concentrate the polycarbonate solution and dry the solution (Japanese Patent Publication No. 53-15899). ii) A method in which a polycarbonate solution is supplied together with a polycarbonate seed powder and a poor solvent or a gas thereof to a granulation tank equipped with a helical stirring blade, and the mixture is heated while stirring and mixing to evaporate and remove the organic solvent and the poor solvent (JP-A-6-100).
No. 703) The shape of the polycarbonate powder may be any shape such as a sphere, a cylinder (pellet shape), or a granular shape, or an amorphous shape. The average particle size of the polycarbonate powder is preferably about 1-10 mm. The reason is that when the average particle diameter is less than 1 mm, a considerable amount of fine powder is originally present in the polycarbonate powder, and the effect of the present invention is to reduce the amount of fine powder to maintain the particle size distribution and bulk density of the powder. This is because it is difficult to obtain, and if it exceeds 10 mm, it becomes difficult to remove the organic solvent contained in the polycarbonate powder.

In the present invention, the content of the organic solvent in the polycarbonate powder to be dried is limited to more than 30% by weight and 60% by weight or less. The reason is that if the content of the organic solvent in the polycarbonate powder exceeds 60% by weight, the powder becomes lumpy when dried, and the powder is dried while maintaining the particle size distribution and bulk density of the powder. If the content of the organic solvent in the polycarbonate powder or granular material is 30% by weight or less, fine powder is not originally generated when the powder or granular material is dried. Therefore, it is necessary to carry out the method of the present invention. Because there is no.

As described above, the method for producing a polycarbonate powder or granular material according to the present invention comprises a polycarbonate powder or granular material having an organic solvent content of more than 30% by weight and 60% by weight or less and a solvent content of at least 30% by weight. Until that time, a primary drying step is performed in which the drying rate calculated by the following equation is set to 0.01 [log (wt%) / min] or less.

Drying rate (Rd) = (log Ca ₁ -log C
a ₂ ) / (t ₂ −t ₁ ) t ₁ , t ₂ : indicates the measurement time point, and t ₂ > t ₁ . Ca _1, Ca _2: shows solvent content of the polycarbonate powder or granular material at time t _1, t ₂ (% by weight).

By drying the polycarbonate powder at a drying rate of 0.01 [log (wt%) / min] or less until the solvent content becomes at least 30% by weight,
Generation of fine powder due to destruction of the polycarbonate powder is suppressed, and as a result, a dry polycarbonate powder having the same particle size distribution and high density as before drying and having a significantly reduced organic solvent content can be obtained. On the other hand, the solvent content is 30% by weight
When above, the drying rate is 0.01 [log (wt%)
/ Min], the polycarbonate powder is destroyed, and changes in particle size distribution and bulk density cannot be avoided.
This is the reason why the drying rate in the primary drying step is limited to 0.01 [log (wt%) / min] or less in the present invention.

The drying rate is 0.01 [log (wt%) / min
The drying temperature in the following primary drying step is not particularly limited, but it is preferably 40 to 120 ° C. under normal pressure, and 30 to 100 ° C. under reduced pressure. Further, the drying time in the primary drying step is 20 to 180.
It is preferably about one minute.

The particle destruction rate of the polycarbonate powder particles after the primary drying step is calculated by the following formula: particle destruction rate (% by weight) = (weight of destroyed powder particles) /
It is calculated by (weight of all powder and granules) × 100, but the particle destruction rate after the primary drying step is preferably 10% by weight or less. The reason for this is that if the particle destruction rate exceeds 10% by weight, the amount of fine powder becomes relatively large, and the particle size distribution and bulk density of the powdery particles change as compared with those before drying.

In the method for producing a polycarbonate powder granule of the present invention, the secondary drying step is performed after the content of the organic solvent in the polycarbonate powder granule becomes at least 30% by weight in the above primary drying step. You can

The drying rate in this secondary drying step does not have to be a special drying rate as in the primary drying step, and can be any drying rate. The reason is that the content of organic solvent in the polycarbonate powder is 30
This is because if the content is less than 10% by weight, even if the drying speed is arbitrary, the generation of fine powder due to the destruction of the polycarbonate powder is unlikely to occur, and therefore the particle size distribution and bulk density of the polycarbonate powder do not change.

The drying temperature in the secondary drying step is not particularly limited, but it is preferably 40 to 150 ° C. under normal pressure and 30 to 150 ° C. under reduced pressure, and the drying time is also not particularly limited. , 60 to 240 minutes is preferable.

Unlike the method described in JP-A-6-155466, which requires the use of a non-blade type stirrer, in the present invention, the dryer used in the primary drying step and the secondary drying step is particularly Without limitation, any airfoil and non-airfoil dryer can be used. Specific examples of such a dryer include a paddle dryer,
A rotary stirring dryer, a drum dryer, a fluid dryer, etc. are mentioned.

As described above, according to the method for drying polycarbonate powder granules of the present invention, the amount of the powder exceeds 30% by weight and 60% or more.
Primary drying for drying a polycarbonate powder containing an organic solvent in an amount of not more than 10% by weight at a drying rate (Rd) of 0.01 [log (wt%) / min] or less until the content of the solvent becomes at least 30% by weight. By performing the process, the generation of fine powder due to the destruction of the powder or granules is suppressed, and the particle size distribution and bulk density are almost the same as those of the polycarbonate powder or granules before drying,
Further, it is possible to obtain a dry polycarbonate powder granule having a significantly reduced organic solvent content of, for example, 1000 ppm or less.

[0032]

EXAMPLES The present invention will be further described below with reference to Examples and Examples.

Reference Example Polycarbonate powder and granules were produced in the following manner according to the method described in Example 1 of JP-A-6-100703.

As a polycarbonate, Teflon FN2200 manufactured by Idemitsu Petrochemical Co., Ltd. (viscosity average molecular weight 22,
000) was dissolved in methylene chloride to obtain a methylene chloride solution of polycarbonate (polycarbonate concentration 15% by weight).

On the other hand, 2 kg of polycarbonate powder (Taflon FN-2200 manufactured by Idemitsu Petrochemical Co., Ltd.) was placed in a stirring container (diameter 30 cm) having an effective internal volume of 10 liter and having a helical stirring blade.

Next, a methylene chloride solution of polycarbonate prepared in advance was supplied to the above stirring container at a rate of about 4-4.5 kg / hr and heptane at a rate of about 0.8-1.0 kg / hr.

The temperature inside the stirring container was adjusted to about 100 ° C. by passing warm water through a jacket provided in the stirring container, and the internal pressure of the stirring container was set to normal pressure.

Three hours after starting the supply of the methylene chloride solution of polycarbonate and heptane, the level of powder and granules inside the container started to rise, so the produced polycarbonate powder and granules were discharged through the outlet valve at the bottom of the container. I pulled it out.
About 14 hours after starting the extraction of the polycarbonate powder, the properties of the powder began to stabilize, so the extracted polycarbonate powder was collected and used for the drying treatment in Examples and Comparative Examples described later. .

Table 1 shows the properties (organic solvent content, average particle size, bulk density) of the polycarbonate powder particles obtained in this Reference Example and used for the drying treatment in Examples and Comparative Examples described later. The properties (organic solvent content, average particle size, bulk density) among the 5 types of polycarbonate powders shown in Table 1 are different because the production batches of the 5 types of polycarbonate powders are different as described above. This is because the flow rates of the methylene chloride solution of polycarbonate and peptane change.

Example 1 As shown in Table 1, a polycarbonate powder having a solvent content of 45% by weight, an average particle size of 1.10 mm and a bulk density of 0.57 g / cc was completely mixed and stirred in a dryer. And the drying rate (Rd) calculated by the above formula is 0.008.
[Log (wt%) / min] and under pressure of -50 mmHg 7
The mixture was stirred at 5 ° C for 2 hours and subjected to primary drying treatment. The conditions for the primary drying treatment are also shown in Table 2.

By the primary drying treatment, as shown in Table 1, the organic solvent content was 28% by weight, the average particle size was 1.08 mm, the bulkiness was 0.57 g / cc, and the particle destruction rate was 3.5%. A polycarbonate powder was obtained.

By the primary drying treatment, the organic solvent content of the powder and granules was reduced from 45% by weight to 28% by weight, but the average particle diameter of the powder and granules was reduced from 1.10 mm to 1.08 mm. There was almost no change, and the bulk density was 0.57 g / cc both before and after the primary drying treatment, showing no change. Further, since the particle destruction rate is as low as 3.5%, it can be seen that the generation of fine powder due to the destruction of the granular material is significantly suppressed.

The polycarbonate powder granules after the primary drying treatment were put into a paddle dryer, and under reduced pressure of -50 mmHg 1
Secondary drying treatment was performed at 40 ° C. for 2 hours. The conditions for this secondary drying treatment are also shown in Table 2. The polycarbonate powder after the secondary drying treatment has an organic solvent content of 0.03% by weight,
The average particle size was 1.05 mm, the bulk density was 0.57 g / cc, the particle destruction rate was 3.5%, and the organic solvent content was significantly reduced to 0.03% by weight due to the secondary drying treatment. The average particle size was almost the same as the average particle size before drying and after the primary drying treatment, and the bulk density was the same as the bulk density before drying and after the primary drying treatment. The particle destruction rate was also extremely low at 3.5%.

Example 2 As shown in Table 1, a polycarbonate powder having an organic solvent content of 41% by weight, an average particle size of 0.86 mm and a bulk density of 0.55 g / cc was used. As shown in Table 2, the drying rate (Rd) was 0.010 [log (wt
%) / Min] and the other conditions of the primary drying treatment and the secondary drying treatment were changed as shown in Table 2, and the polycarbonate powder was dried in the same manner as in Example 1.

Table 1 shows the properties of the granular material after the primary drying treatment and the properties of the final granular material after the secondary drying treatment. As is clear from Table 1, the content of the organic solvent is as low as 0.05% by weight, the average particle size and bulk density are the same or substantially the same as those of the powder before drying, and the particle destruction rate is The final granules obtained were extremely low at 6.5%.

Example 3 As shown in Table 1, a polycarbonate powder having an organic solvent content of 45% by weight, an average particle size of 1.23 mm and a bulk density of 0.52 g / cc was used in the primary drying treatment. Table 2 shows that the drying rate (Rd) was set to 0.009 [log (wt%) / min] using a paddle dryer as shown in Table 2 and other conditions for the primary drying treatment and the secondary drying treatment. Polycarbonate powder was dried in the same manner as in Example 1 except that the above was changed.

Table 1 shows the properties of the granular material after the primary drying treatment and the properties of the final granular material after the secondary drying treatment. As is clear from Table 1, the content of the organic solvent is as low as 0.05% by weight, the average particle size and bulk density are the same or substantially the same as those of the powder before drying, and the particle destruction rate is The final powder and granules obtained were as low as 5.0%.

Comparative Example 1 As shown in Table 1, a polycarbonate powder having an organic solvent content of 42% by weight, an average particle size of 1.81 mm and a bulk density of 0.44 g / cc was charged into a paddle dryer, As shown in Table 2, the drying rate exceeds the limit value of the present invention of 0.01
7 [log (wt%) / min] and dried at 135 ° C. for 4 hours under a pressure of −50 mmHg.

Table 1 shows the properties of the final granules obtained after the drying treatment. As is clear from Table 1, the particle size of the powder before drying was 1.81 mm, while the average particle size of the final powder was 1.23 mm, which was a marked decrease. This is because the powder and granules were destroyed during the drying, and a large amount of fine powder was generated, which is also supported by the data of the particle destruction rate of 50.0% shown in Table 1. The bulk density is 0.44 g / cc before drying.
It was changed to 0.52 g / cc after drying.

Comparative Example 2 As shown in Table 1, a polycarbonate powder having an organic solvent content of 46% by weight, an average particle size of 1.57 mm and a bulk density of 0.48 g / cc was put into a paddle dryer, As shown in Table 2, the drying rate exceeds the limit value of the present invention of 0.01
6 [log (wt%) / min] and dried at 125 ° C. for 4 hours under a pressure of −50 mmHg.

Table 1 shows the properties of the final granules obtained after the drying treatment. As is clear from Table 1, the particle size of the powder and granules before drying was 1.57 mm, while the average particle size of the final powder and granule was 1.11 mm, which was a marked decrease. This is because the powder and granules were destroyed during the drying, and a large amount of fine powder was generated, which is also supported by the data of the particle destruction rate of 45.0% shown in Table 1. The bulk density is 0.48 g / cc before drying.
It was changed to 0.56 g / cc after drying.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

EFFECTS OF THE INVENTION According to the present invention, the solvent contained in the polycarbonate powder or granules can be mixed with the solvent contained in the polycarbonate powder or granules by using an arbitrary dryer including a conventionally used blade dryer. A method has been provided whereby the polycarbonate can be dried at low cost by removing it without changing its density.

Claims (7)

[Claims] 1. A drying rate calculated by the following formula is 0.01 [for a polycarbonate powder containing an organic solvent in an amount of more than 30% by weight and not more than 60% by weight, until the solvent content becomes at least 30% by weight. log (wt%) / min] or less, and a primary drying step of drying the polycarbonate powder granules. Drying rate _{(Rd) = (log Ca 1} -log Ca 2) / (t
_{2 -t 1) t 1, t} 2: shows a measurement point, which is t _2> t _1. Ca _1, Ca _2: shows solvent content of the polycarbonate powder or granular material at time t _1, t ₂ (% by weight). 2. The method of claim 1, wherein the polycarbonate granules have an average particle size of 1-10 mm. 3. The method according to claim 1, wherein the primary drying step is carried out under normal pressure at 40 to 120 ° C. or under reduced pressure at 30 to 100 ° C. for 20 to 180 minutes. 4. The particle destruction rate of the polycarbonate powder granules after the primary drying step is 10% by weight calculated by the following formula.
The method of claim 1, wherein: Particle destruction rate (% by weight) = (weight of destroyed particles) /
(Weight of all granules) x 100 5. The method according to claim 1, wherein the secondary drying step is performed after the primary drying step. 6. The method according to claim 5, wherein the secondary drying step is carried out under normal pressure at 40 to 150 ° C. or under reduced pressure at 30 to 150 ° C. for 60 to 240 minutes. 7. The method according to claim 1 or 5, wherein the primary drying step and the secondary drying step are performed using a paddle dryer, a rotary stirring dryer, a drum dryer, a fluidized dryer and the like.