JPH07233251A - Production of polyester - Google Patents

Abstract

PURPOSE:To provide a production process whereby the discharge of the product from the polycondensation reactor can be smoothly performed, and a high-quality polyester can be produced at good efficiency by keeping the temperature of the heating medium in the stage of reaction and that in the stage of discharging in specified ranges. CONSTITUTION:This production process is one for producing a polyester by polycondensation under agitation in a batchwise polycondensation reactor provided with a heating jacket. This process comprises keeping the temperature of the heating medium at a temperature ranging from the melting point of the polyester minus 40 deg.C to the melting point in the stage of removing the heat of agitation in the course of the polycondensation reaction, and keeping the temperature of the heating medium at a temperature ranging from the melting point of the polyester to the melting point plus 20 deg.C. In a particular actual example, the polycondensation reaction is started under high-speed agitation, the temperature of the heating medium is lowered when the temperature of the polymer reaches a specified temperature, the reaction is continued under conditions of heat removal, and at the same time the temperature of the polymer is made uniform by gradually lowering the rotation speed of the agitating element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing polyester by a batch polycondensation reaction.

[0002]

2. Description of the Related Art As a method for producing polyester, there are a continuous method and a batch method. The former is for mass production of a single brand,
The latter is suitable for small-scale production. In recent years, polyesters having various characteristics have been demanded, and a batch type suitable for small lot production of many brands is being reviewed.

When the polyester is produced batchwise, the polycondensation reaction is carried out with stirring using a batch polycondensation reactor equipped with a heating medium jacket, but the heat of stirring increases as the polycondensation reaction proceeds. However, the temperature of the polyester at the end of the reaction is high, and the polyester is easily deteriorated by heat.

In order to solve this problem, a method of decreasing the stirring speed as the polycondensation reaction proceeds is generally adopted. FIG. 3 shows a model of changes over time in the heat medium temperature, the stirring blade rotation speed, and the polymer temperature in the conventional method. When the stirring speed is reduced as described above, the stirring effect is reduced and it is necessary to lengthen the time of the polycondensation reaction. In order to suppress the temperature rise of the polyester without lowering the stirring speed, it is necessary to remove heat efficiently. In order to increase the heat removal capacity, there is a method of installing a cooling coil in the reactor to increase the heat transfer area, but this method deteriorates the fluidity of the polyester in the polycondensation reactor and increases the heat removal capacity. There is a problem that the polyester does not increase so much or that the polyester deteriorates due to drift. Further, as a method for increasing the heat removal capacity, there is also a method of lowering the temperature of the heating medium, but this method has a problem that the polyester remains in the reactor when the polyester is discharged from the polycondensation reactor. However, the heat medium temperature could not be lowered so much.

[0005]

DISCLOSURE OF THE INVENTION The present invention efficiently removes heat of stirring when producing a polyester by carrying out a polycondensation reaction with stirring using a batch type polycondensation reactor equipped with a heating medium jacket. And, the polyester can be smoothly discharged from the polycondensation reactor,
An object of the present invention is to provide a polyester production method capable of efficiently producing high-quality polyester.

[0006]

Means for Solving the Problems The present invention is intended to solve the above problems, and its gist is to carry out a polycondensation reaction with stirring using a batch polycondensation reactor equipped with a heating medium jacket. In the production of polyester, in the step of removing heat of stirring during the polycondensation reaction (cooling step), the temperature of the heat medium is lower than the melting point of polyester and kept at a temperature not lower than the melting point minus 40 ° C, and the polyester is discharged from the reactor. The temperature of the heating medium is higher than the melting point of the polyester in the discharging step,
A method for producing a polyester is characterized in that the temperature is kept at a melting point plus 20 ° C. or lower.

The present invention will be described in detail below. The method of the present invention includes polyethylene terephthalate, polybutylene terephthalate and isophthalic acid, 5-sodium sulfoisophthalic acid, diethylene glycol,
It can be applied to the production of various polyesters such as polyesters copolymerized with polyethylene glycol and neopentyl glycol.

FIG. 1 is a schematic view showing an example of a batch-type polycondensation reaction apparatus used for carrying out the present invention. 1 is a polycondensation reactor, 2 is an oligomer supply pipe, 3 is an additive such as a catalyst. A tube, 4 is a stirring blade, 5 is a heating medium jacket, 6 is a vacuum suction tube, and 7 is a polymer delivery tube. Heat medium jacket 5
The heat medium is supplied to the heater by a heat medium pump 8, and the heat medium extracted from the heat medium jacket 5 is sent to a heater 10 or a cooler 11 via a pipe 9 and a heat medium pump via a control valve 12. It is sent to the No. 8 and the heat medium is circulated.

In the present invention, the temperature of the heat medium and the rotation speed of the stirring blade are changed with time as shown in a model in FIG.
The polymer temperature is kept constant.

In order to carry out the method of the present invention, first, the temperature of the heating medium is increased to increase the temperature in the polycondensation reactor to accept the oligomer, but the initial temperature of the polymer (oligomer) is low due to the acceptance of the oligomer. It becomes a standard. The polycondensation reaction is started under high-speed stirring, and when the polymer temperature rises to reach a predetermined temperature (reaction temperature), the heat medium temperature is lowered and the polycondensation reaction proceeds while removing heat. If high-speed stirring is continued, the amount of stirring heat generated increases and the polymer temperature rises with the progress of the reaction even if the heating medium temperature is lowered,
The rotation speed of the stirring blade is gradually reduced so that the polymer temperature becomes constant. When the polymer reaches a predetermined degree of polymerization (intrinsic viscosity), the temperature of the heating medium is raised, stirring is stopped, and the polymer is discharged.

The temperature of the heating medium in the cooling step is lower than the melting point of the polyester, and it is necessary to maintain the temperature at the melting point minus 40 ° C. or higher (preferably the melting point minus 20 ° C. or higher). When the temperature of the heat medium is lower than this, the high melting point substance of polyester adhering to the inner wall of the reactor is peeled off and becomes a foreign substance and mixed in the product, and the quality is deteriorated.

Further, the temperature of the heating medium in the payout stage is higher than the melting point of the polyester, and it is necessary to keep the temperature at the melting point plus 20 ° C. or lower. If the temperature of the heating medium is higher than this, the polyester being dispensed will be overheated and the thermal decomposition will proceed, deteriorating the quality.

[0013]

According to the method of the present invention, since the heat of stirring can be efficiently removed, the reaction time under high speed stirring can be lengthened and the reaction speed can be increased, so that high quality polyester can be efficiently produced. Can be manufactured in a simple manner. Further, since the polymer can be discharged smoothly, the amount of the polymer remaining in the reactor can be reduced and the yield can be improved.

[0014]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The polymers were evaluated in the examples as follows. (1) Intrinsic viscosity [η] It was measured at a temperature of 20 ° C using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (2) b value (color tone) It was measured using a colorimeter 300A manufactured by Nippon Denshoku Industries Co., Ltd. (3) Melting point Using a differential scanning calorimeter DSC-2 type manufactured by Perkin Elmer Co.,
It was measured at a temperature rising rate of 20 ° C./min. (4) Amount of foreign matter About 100g of pellets (about 0.3g per pellet)
The number of pellets containing a foreign substance having a diameter of 1 mm or more was counted visually.

Example 1 2000 kg of bis (β-hydroxyethyl) terephthalate obtained by the esterification reaction of terephthalic acid with ethylene glycol and its low polymer (oligomer) 2000 kg, and 2% by weight of antimony trioxide as a polycondensation reaction catalyst. 30 kg of ethylene glycol solution was charged into the polycondensation reactor shown in FIG. 1, and the polycondensation reaction was started with the heating medium temperature of the jacket at 310 ° C., the rotating speed of the stirring blades at 40 rpm, and the ultimate vacuum degree of 0.2 torr. The temperature of the polyester (reaction temperature) is 1.0 hours after the start of the reaction.
Since the temperature reached 285 ° C, the heat medium temperature was lowered to 240 ° C and the polycondensation reaction was continued. The temperature of the stirring blade was gradually reduced as the polycondensation progressed so that the reaction temperature became constant at 285 ° C from the 1.0th hour after the heat medium temperature was lowered to 240 ° C. After reaching 8 rpm, the rotation speed was constant. The reaction continued as a number. Intrinsic viscosity is 0.
The reaction was terminated when the temperature reached 74 (3.0 hours after the temperature of the heating medium was lowered to 240 ° C). Then, the heating medium temperature was raised to 260 ° C., the stirring was stopped, and the polymer discharge was started.
The payment was completed in time. The discharged polymer was discharged in a strand shape, cooled and solidified, and then cut into pellets.

Example 2 The heating medium temperature in the cooling step was 225 ° C.
It carried out according to.

Example 3 The heating medium temperature at the payout stage was set to 270 ° C., and the other conditions were the same as in Example 1.

Example 4 An oligomer obtained from a mixture of terephthalic acid and isophthalic acid in a molar ratio of 92/8 and ethylene glycol was used, the heat medium temperature in the cooling step was 225 ° C, and the heat medium in the payout step was The temperature was set to 260 ° C., and the other conditions were the same as in Example 1.

Example 5 Example 5 was repeated except that the oligomer obtained by the transesterification reaction of dimethyl terephthalate and ethylene glycol was used.

Example 6 An oligomer obtained from ethylene glycol and a mixture of terephthalic acid and 5-sodium sulfoisophthalic acid in a molar ratio of 95/5 was used, the reaction temperature was 275 ° C., and the heating medium temperature in the cooling stage was used. 230 ℃, heating medium temperature at the payout stage is 2
The temperature was set to 50 ° C., and the other conditions were the same as in Example 1.

Example 7 2000 kg of an oligomer obtained from dimethyl terephthalate and 1,4-butanediol and 10 kg of a 4% by weight solution of tetrabutyl titanate in 1,4-butanediol as a polycondensation reaction catalyst were used. Medium temperature 260 ° C, reaction temperature 2
The heating medium temperature was 40 ° C., the heating medium temperature was 210 ° C. in the cooling stage, the heating medium temperature was 230 ° C. in the paying-out stage, and other conditions were the same as in Example 1.

Comparative Example 1 The same procedure as in Example 1 was repeated except that the temperature of the heat medium in the cooling step was 260 ° C. and the rotation speed of the stirring blade was gradually decreased so that the reaction temperature became constant as soon as the cooling step was started. did.

Comparative Example 2 Example 1 except that the heating medium temperature at the payout stage was 240 ° C.
It carried out according to.

Comparative Example 3 Example 1 except that the heating medium temperature at the payout stage was 285 ° C.
It carried out according to.

The results of the above Examples and Comparative Examples are shown in Tables 1 and 2.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

EFFECTS OF THE INVENTION According to the present invention, the heat of stirring is efficiently removed when a polyester is produced by carrying out a polycondensation reaction with stirring using a batch-type polycondensation reactor equipped with a heating medium jacket. In addition, the polyester can be smoothly discharged from the polycondensation reactor, and high-quality polyester can be efficiently produced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a batch-type polycondensation reaction apparatus used for carrying out the present invention.

FIG. 2 is a model view showing changes over time in the heat medium temperature, the stirring blade rotation number, and the polymer temperature in the present invention.

FIG. 3 is a model view showing changes with time of a heating medium temperature, a stirring blade rotation number, and a polymer temperature in a conventional method.

[Explanation of symbols]

 1 Polycondensation reactor 4 Stirring blade 5 Heat medium jacket 8 Heat medium pump 10 Heater 6 Cooler

Claims (1)

[Claims] 1. When producing a polyester by carrying out a polycondensation reaction with stirring using a batch-type polycondensation reactor equipped with a heat medium jacket, the heat medium is removed in the step of removing heat of stirring during the polycondensation reaction. Temperature below the melting point of the polyester and above the melting point minus 40 ° C. At the stage of discharging the polyester from the reactor, keep the temperature of the heat medium above the melting point of the polyester and below the melting point plus 20 ° C. And a method for producing a polyester.