JP2888769B2 - Method for producing polymer granules - 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 polymer granules. More specifically, the present invention relates to a method for efficiently producing polymer particles by bringing a solution of a polymer organic solvent such as polycarbonate into contact with a polymer powder under a condition of easy volatilization.

[0002]

2. Description of the Related Art Polymers can be obtained in various states such as a solution state, an emulsified state, and an irregularly shaped powdery granule through a polymerization process, and these are immediately used as raw materials for various molding processes such as extrusion molding and injection molding. It is difficult to use, and usually, it is first formed into a granular material having a predetermined shape and size, and this is supplied to a raw material for forming. However, since these granules are intermediates for the production of final polymer compacts, they must be manufactured using simpler and cheaper processes and have high quality without using complicated and expensive special equipment as much as possible. Is desired.

[0003] The prior art will be described in detail using polycarbonate as an example of a polymer. (i) A method in which the polymer solution obtained by the polycarbonate polymerization process is pulverized while removing the solvent using a special device such as a kneader (Japanese Patent Publication No. 53-15899).
However, this is not preferable because the equipment cost is high and the processing capacity is limited. (ii) A method of performing granulation in a general vertical tank (JP-A-6-10
However, in the case of scale-up, there is a problem that a heat transfer area with respect to a processing amount is reduced and a heat load is increased. (iii) There is a method in which heptane or the like as a poor solvent is vaporized and supplied to a granulation tank to obtain heat input (Japanese Patent Application Laid-Open No. 5-78494). However, the vaporized heptane or the like is not sufficiently dispersed. In some cases, the solution passes through the tank, in which case the solvent removal for granulation is uneven and the removal efficiency is not good. (iv) The concentration of the methylene chloride solution in the polycarbonate depends on the temperature and pressure in the heat exchanger or pipes, but is about 35%.
When it is about 45% by weight, the polymer gels and handling becomes difficult.

[0004]

Accordingly, the present invention relates to a method of granulating a polymer from a solution of the polymer in an organic solvent,
To solve problems mainly related to granulation equipment, such as limitation of processing capacity, heat load due to scale-up, abnormal increase of equipment cost, gelation at high concentration of organic solvent solution of polymer, etc. It is.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve these problems, and as a result, have been able to solve the problem by supplying a polymer organic solvent solution under specific conditions to heated polymer powder. The inventors have found that the present invention has been completed and completed the present invention.

That is, the gist of the present invention is as follows. (1) In a method for producing polymer granules from an organic solvent solution of a polymer, the organic solvent solution of the polymer is heated under pressure with a heat exchanger, and is passed through a flash valve.
A polymer powder of the same type as the polymer is heated under atmospheric pressure and flashed in a uniformly stirred granulation tank,
A method for producing polymer granules while removing a solvent. (2) The method for producing a polymer granule according to the above (1), wherein the polymer is one polymer selected from polycarbonate, polyarylate, polyester polycarbonate and polyamide. (3) The method for producing polymer granules according to the above (1), wherein the organic solvent solution of the polymer is a methylene chloride solution of polycarbonate. (4) Methylene chloride solution of polycarbonate is 10
The method for producing polymer granules according to the above item 3, wherein the polymer granules are 30% by weight and the concentration after flashing is 35 to 60% by weight. (Fifth) Under a pressure of ² to ²⁰ kg / cm ² G with a heat exchanger,
5. The method for producing polymer granules according to the third or fourth aspect, wherein the method is carried out by heating to 40 to 150 ° C.

Hereinafter, the contents of the present invention will be described in detail. In the present invention, the target polymer is most preferably polycarbonate or polyarylate, but it is also possible to use various polymers produced by solution polymerization, such as polyester polycarbonate and polyamide.

Among them, for example, a solution of a polycarbonate in an organic solvent is obtained by a usual polycondensation reaction and can be easily produced by reacting a dihydric phenol with a phosgene or carbonate compound. Here, examples of the dihydric phenol include hydroquinone; 4,4′-dihydroxydiphenyl; bis (4-hydroxyphenyl) alkane (such as bisphenol A); bis (4-hydroxyphenyl) cycloalkane; Phenyl) oxide; bis (4-hydroxyphenyl) sulfide; bis (4-hydroxyphenyl) sulfone; bis (4-hydroxyphenyl) ketone, and halogen-substituted compounds thereof.

Examples of the carbonate compound include diaryl carbonates such as diphenyl carbonate, and dialkyl carbonates such as dimethyl carbonate and diethyl carbonate. The most commonly used polycarbonate obtained by the phosgene method of reacting phosgene with a dihydric phenol is bisphenol A and phosgene formed from tertiary amine (such as triethylamine) in an inert solvent such as methylene chloride (methylene chloride). It can be obtained by reacting in the presence of a catalyst.

The polyarylate organic solvent solution is obtained by a usual polycondensation reaction, and can be easily produced by reacting a dihydric phenol with terephthalic acid dichloride, isophthalic acid dichloride or the like. Here, examples of the dihydric phenol include the same compounds as in the case of the above polycarbonate.

The organic solvent used in the present invention may be any organic solvent which is substantially inert to the polymer, is substantially stable at the use temperature, and dissolves the polymer. However, when a solvent having a high boiling point is used, it is naturally necessary to increase the temperature of the polymer solution in order to efficiently perform devolatilization of the solvent, which may cause a chemical change of the polymer, and the like. Therefore, in consideration of removal of the organic solvent from the polymer granules, it is preferable to use an organic solvent having a boiling point of 200 ° C. or lower. Examples of the organic solvent include, for polycarbonate, methylene chloride, which is usually preferably used, and chlorine-based solvents such as chloroform and chlorobenzene.

The above-mentioned organic solvent used in the present invention may contain a poor solvent which does not precipitate a polymer in order to improve the releasability of the organic solvent. It may be supplied to powder. In this case, in addition to the method of supplying the liquid, a method of supplying the vaporized vapor is preferably employed. As the poor solvent used, heptane, hexane, aliphatic hydrocarbons such as pentane,
Aromatic hydrocarbons such as benzene, toluene and xylene,
In addition to ketones such as acetone and methyl ethyl ketone, ethyl acetate, dioxane, tetrahydrofuran and the like can be mentioned. Among these, aliphatic or aromatic hydrocarbons having 5 to 10 carbon atoms are preferably used in terms of operability, detachability from the polymer, and other costs.

In the present invention, the polymer powder previously supplied into the granulation tank is not only the same kind of polymer as the granular material to be obtained by the production method according to the present invention, but also the practically desired granular material. As long as there is almost no influence on the physical properties of the polymer, there are also included polymer powders having different comonomer units and having different degrees of polymerization or different distribution. The powder itself may be obtained by any production method, but it is preferable that the particle size is the same as that of the target granular material of the present invention because the product can be obtained immediately after the start of granulation.

Next, FIG. 1 shows an example of a production process of the polymer particles of the present invention. In FIG. 1, a polymer organic solvent solution 1 is heated and pressurized in a heat exchanger 2, and is passed through a flash valve 3 connected by a pipe 8 equipped with a pressure gauge P and a thermometer T and a subsequent pipe 9 and a granulation tank 4. Flushed to This granulation tank is provided with a jacket 5 and a stirrer 7 with stirring blades 6. The polymer organic solvent solution 1 and the poor solvent 10 are supplied from supply ports A and B, respectively,
The organic solvent vapor 11 and the generated granular material 12 are discharged from outlets C and D, respectively.

The production of the polymer particles according to the present invention is carried out by heating a solution of the polymer in an organic solvent under pressure with a heat exchanger and flashing the solution in a granulation tank through a flash valve. The concentration of the organic solvent solution is preferably concentrated to about 10 to 30% by weight. If the solution supplied to the heat exchanger is less than 10% by weight,
The amount of the solvent that is removed by heating in the granulation tank and sent to the recovery device increases, which is inefficient in terms of calorific value. Conversely, 30% by weight
If it exceeds, gelation of the polymer in the heat exchanger and piping,
Precipitation is likely to occur, and the solution supply operation may be difficult due to a decrease in fluidity, which is not preferable. The above-mentioned concentration adjustment of the organic solvent solution of the polymer can be easily performed by various known means such as a flash drum.

The heating temperature of the polymer organic solvent solution by the heat exchanger is preferably not lower than the boiling point of the solvent used under normal pressure. This is because it is preferable that the temperature is such that it can be efficiently evaporated and removed when the atmosphere is flashed to a normal pressure atmosphere. In addition, the higher the solution temperature, the lower the temperature of the polymer powder in the granulation tank is prevented, or the temperature of the polymer powder in the granulation tank is further increased, and the decrease in the amount of residual solvent of the polymer in the granulation tank reduces the stirring torque of the stirrer. It will also be. However, 20
A temperature of about 0 ° C. or higher is not preferred because the solvent is likely to be decomposed in addition to polymer deterioration. In the case of a methylene chloride solution of polycarbonate, the temperature is preferably 40 to 150 ° C.
0-140 ° C is particularly preferred.

The pressure at which the polymer organic solvent solution is pressurized by the heat exchanger is preferably at least the vapor pressure of the organic solvent at the above-mentioned heating temperature or about three times the vapor pressure. If the pressure is lower than the vapor pressure, the concentration becomes high, and the polymer is liable to precipitate and gel. However, when the pressure is increased to about three times the vapor pressure, it is necessary to consider the problems of the pumping capacity and the pressure limit of the piping more than in the case of using in a normal industrial process, and the inefficiency arises. It is a target. In the case of a methylene chloride solution of polycarbonate, ^{2 to 20} kg / cm ²
A pressure of about G is preferred, but 11 to 13 kg / cm
^A pressure condition of ² G is particularly preferred.

Naturally, the heat exchanger used here must be able to withstand the above-mentioned heating temperature and pressurizing pressure. When using methylene chloride as a solvent, at least 200 ° C., 50 kg / m It is sufficient that the material can withstand the condition of about cm ² G. Further, the material of the inner wall of the heat exchanger must have corrosion resistance to the polymer to be treated and its solvent at least at the above-mentioned operating temperature and pressure. When a usual polymer or solvent is used, stainless steel is sufficient, but it is also preferable to provide a ceramic lining such as a glass lining on the inner wall.

The type of the heat exchanger used is not particularly limited, and generally used double tube heat exchangers, multi-tube heat exchangers, plate heat exchangers and the like are used. Although possible, a multi-tube heat exchanger is particularly preferably used. The structure of the heat exchanger will be described in the case of a multi-tube heat exchanger. The heat exchanger is composed of a fixed part, a torso, and an occiput, and each part has several different structures. Alternatively, a structure that facilitates maintenance such as cleaning after that is preferable.
Specifically, a one-pass type or a two-pass type in which the fixed portion and the back of the head can be removed is preferably applied.

The structure of the flash valve used in the present invention is not particularly limited, and various structures such as a gate valve, a globe valve, a check valve, a plug valve, a ball valve, a butterfly valve, a diaphragm valve and the like can be used. Is used as appropriate, the inlet side is a side for receiving the polymer organic solvent solution discharged from the heat exchanger, the temperature of the solution, it is necessary to withstand the same conditions as the pressure, as a specific example, If methylene chloride is a solvent for polycarbonate, at least 2
It is required to withstand 00 ° C. and 50 kg / cm ² .
Further, the flash valve as a whole is required to have the same corrosion resistance as the heat exchanger. The means for adjusting the opening degree of the valve may be a commonly used means such as a pneumatic type or an electric type, and the inlet side is adjusted so that at least the pressure and temperature of the heat exchanger can be maintained. The pipe connecting the flash valve and the granulation tank is preferably as short as possible because the polymer organic solvent solution may be flushed and the concentration may increase, the temperature may decrease and the pipe may be blocked.

By passing through the flash valve, the polymer organic solvent solution is concentrated. The degree of concentration depends on the solvent recovery efficiency, the state of clogging of the pipe, the particle growth rate centering on the polymer powder in the granulation tank, and the particle size. In consideration of the shape, the stirring torque of the stirrer, and the like, the concentration is preferably about 35 to 60% by weight. If the amount is less than 35% by weight, the effect of reducing the heat load and other effects due to the use of the heat exchanger and the flash valve cannot be sufficiently obtained. In addition to this, undesirable results such as an increase in the stirring torque of the stirrer are produced.

The polymer organic solvent solution that has passed through the flash valve is supplied to a granulation tank in which the same polymer powder heated to a temperature equal to or higher than the boiling point of the organic solvent under atmospheric pressure is stirred. The polymer organic solvent solution is concentrated by the rapid evaporation of the solvent under the atmospheric pressure and is supplied to the granulation tank, whereby a granular material having less residual solvent is formed. Even if the previously supplied polymer powder is consumed as a granulation seed, the granulation operation is continuously performed because new, small granules are simultaneously generated in a heated state by stirring. obtain.

The supply amount of the polymer organic solvent solution is not particularly limited and cannot be uniquely determined, but is preferably hourly based on the amount of the polymer powder that is uniformly stirred and present in the container. It is 250% by weight or less, more preferably 100% by weight or less per hour. When the supply amount is small, the productivity is decreased, and when the supply amount is large, the amount of the residual solvent in the obtained polymer granules increases, which is not preferable.

The method of supplying the flushed polymer organic solvent solution may be such that the solution is dropped or dropped on the surface of the polymer powder, or may be supplied into a flowing polymer powder. In this case, if the vaporized poor solvent is supplied to the polymer powder simultaneously with the polymer solution, the solvent removal rate can be increased. In this case, it is preferable in terms of granulation efficiency that the polymer solution supply port is provided at a position where the solution is directly supplied to a portion where the polymer powder is present.

A stirrer usually used for stirring a powder is attached to a granulation tank for mixing and granulating the polymer powder. Various types of preferable stirring blades such as a helical blade are also disclosed in JP-A-6-100703, but a paddle blade is also preferably used.

Since the granulation tank needs to keep the polymer powder constantly heated and to promote the desolvation of the supplied concentrated polymer organic solvent solution, at least the inner wall having a heatable structure is required. Preferably, the structure is not particularly limited, but usually a jacketed structure using steam, hot water, oil or the like as a heat source is used.
In addition to the polymer solution and poor solvent supply port in the granulation tank, a solvent vapor outlet port is required above the granulation tank, and a formed polymer particulate material outlet port is required in the bottom of the granulation tank. The vapor outlet is connected to a solvent vapor suction device, a solvent recovery device, and the polymer particulate outlet is connected to the particulate storage device or the drying device.

Next, the present invention will be described with reference to examples.

【Example】

(Example 1) Polycarbonate (manufactured by Idemitsu Petrochemical Co., product name: Teflon FN2200, viscosity average molecular weight: 22,100) was used as a polymer, dissolved in methylene chloride (manufactured by Hiroshima Wako Pure Chemical Industries, special grade) and 10% by weight. A solution of the polymer in an organic solvent, that is, a methylene chloride solution (PCM) was prepared. This PCM was further passed through a flash drum to obtain 30% by weight PCM, and heated and pressurized to 130 ° C. and 12 kg / cm ² G in a single-pass multi-tube heat exchanger (AEL type) having a 1 / 2B internal tube in one pass. . A globe-type control valve was used as a flush valve, and the granulation vessel was flushed through a pipe having a length of 70 cm between the flush valve and the granulation vessel and a pipe diameter of 3 / 4B. The PCM concentration at this time was 52% by weight.
Met. Use a 110-litre vertical container equipped with a helical blade stirrer and a warm water jacket in the granulation tank, and charge about 30 kg of polycarbonate powder in advance. The above PCM was directly added onto the powder at 48.4 ° C. while stirring at 80 rpm under heating while controlling by operation.
kg / hr (based on polycarbonate), and at the same time 5 kg / h of poor solvent heptane from the top of the granulation tank
r. The jacket inlet temperature at that time is 51 ° C
Met. Powder level rises, about 80% of granulation tank volume
, The granular material was intermittently withdrawn from the bottom of the tank to keep the powder level constant. The average particle size during continuous stable operation was 2.20 mm, the liquid content of the granular material [solvent / (solvent + powder)] was 44.4% by weight, and the stirring torque was 6.28 kgm. The experimental conditions and results are summarized in Table 1.

Example 2 PCM having a polymer concentration of 36% by weight was heated and pressurized at 54.2 ° C. and 5 kg / cm ² G.
And the inlet temperature of the granulation tank jacket was 5
The granulation operation was performed under the same conditions as in Example 1 except that the operation was performed at 4 ° C., the polymer powder temperature was 50.0 ° C., and the stirring speed of the granulation tank was 110 rpm. During continuous stable operation, the average particle size of the polymer particles was 1.87 mm, the liquid content of the particles was 43.3% by weight, and the stirring torque was 5.52 kgm. The experimental conditions and results are summarized in Table 1.

Comparative Example 1 P having a polymer concentration of 30% by weight
The CM was passed through a heat exchanger at normal pressure to raise the temperature to 38.8 ° C., without using a flash valve, at a polymer solution pressure of 1 kg / cm ² G based on the back pressure of the pipe, and a jacket inlet temperature of 63.1
A granulation operation was carried out under the same conditions as in Example 1 except that the powder was supplied to a 48.1 ° C. polymer powder layer in a granulation tank at 4 ° C. As a result, the average particle diameter was 2.01 mm, the liquid content was 49.7% by weight, and the stirring torque was 7.21 kgm. The stirring torque was higher than that of Example 1 despite the higher jacket inlet temperature. The experimental conditions and results are summarized in Table 1.

Comparative Example 2 PCM having a polymer concentration of 64% by weight was heated and pressed at 160 ° C. and 20 kg / cm.
^A granulation operation was carried out under the same conditions as in Example 2 except that the temperature at the inlet of the granulation tank jacket was 45 ° C. and the temperature of the polymer powder was 50.0 ° C. through a heat exchanger of ² G. As a result, the average particle size of the polymer granules was 1.72 mm, and the liquid content of the granules was 4
Although it was 0.2% by weight, the viscosity average molecular weight of the polymer changed from 22100 to 20600 due to thermal degradation of the polymer, and a decrease in the molecular weight was observed. The experimental conditions and results are summarized in Table 1.

Comparative Example 3 PCM having a polymer concentration of 35% by weight was heated and pressed at 51 ° C. under 0.5 kg / cm ² G.
The granulation operation was performed under the same conditions as in Example 2 except that the mixture passed through a heat exchanger. As a result, the polycarbonate gelled and precipitated in the pipe, the back pressure of the PCM supply pump gradually increased, the pipe became slightly blocked, and the operation was stopped.
The experimental conditions and results are summarized in Table 1.

[0032]

[Table 1]

[0033]

【The invention's effect】

(1) If PCM is supplied to the granulation tank at low temperature, low pressure and low concentration without using a flash valve, it is necessary to increase the jacket inlet temperature, and unnecessary heat is applied to the polymer. In addition, when the flash valve is not used, the liquid content becomes higher, probably because the evaporation rate of the solvent is slower than when the flash valve is used, and as a result, the stirring torque increases. (Mainly from the results of Example 1 and Comparative Example 1.) (2) Even if a flash valve is used, if the PCM temperature, pressure, and concentration are too high, the jacket inlet temperature and stirring torque are reduced, The viscosity average molecular weight of the polymer decreases due to thermal degradation of the polymer. (Mainly from the results of Example 2 and Comparative Example 2.) (3) At a temperature and pressure at which the solvent of the PCM boils in the pipe before the flash valve, the polymer is precipitated in the valve and the pipe. In addition, blockage of piping and the like occurs, and continuous operation becomes difficult. (Mainly from the results of Example 2 and Comparative Example 3)

[Brief description of the drawings]

FIG. 1 shows an example of a process for producing a polymer particle of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polymer organic solvent solution 2 Heat exchanger 3 Flash valve 4 Granulation tank 5 Jacket 6 Stirrer blade 7 Stirrer 8 Pipe 9 Pipe 10 Poor solvent 11 Organic solvent vapor 12 Generated polymer particulate matter A Polymer organic solvent solution supply port B Poor solvent supply Port C Organic solvent vapor discharge port D Generated particulate matter discharge port P Pressure gauge T Thermometer M Stirrer motor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 3/12-3/14

Claims (5)

(57) [Claims] 1. A method for producing polymer granules from a solution of a polymer in an organic solvent, wherein the solution of the polymer in an organic solvent is heated under pressure by a heat exchanger, and the powder of the same polymer as the polymer is passed through a flash valve. Is heated under atmospheric pressure and flushed into a uniformly stirred granulation tank to remove the solvent and produce polymer granules. 2. The method according to claim 1, wherein the polymer is one polymer selected from polycarbonate, polyarylate, polyester polycarbonate and polyamide. 3. The method for producing polymer granules according to claim 1, wherein the solution of the polymer in an organic solvent is a solution of polycarbonate in methylene chloride. 4. The method according to claim 1, wherein the methylene chloride solution of the polycarbonate is 1
0 to 30% by weight, and the concentration after flash is 35 to 6%.
The method for producing a polymer granule according to claim 3, which is 0% by weight. 5. The process for producing polymer granules according to claim 3, wherein the process is carried out by heating to 40 to 150 ° C. under a pressure of ² to 20 kg / cm ² G in a heat exchanger.