JPH083301A - Production of polyethylene terephthalate having high polymerization degree - Google Patents

Abstract

PURPOSE:To provide a process for producing a polyethylene terephthalate having high quality and polymerization degree without generating flow failure at a gas-liquid interface in polymerization reaction. CONSTITUTION:The polycondensation reaction after an esterification reaction is divided into a former-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [eta] of 0.4-0.9dlambda/g and a latter-stage polycondensation step to get a polyethylene terephthalate having an intrinsic viscosity [eta] of 0.8-1.3dlambda/g. The latter-stage polycondensation is carried out by a stirring polymerizer having plural rotary shafts 12, 13 and stirring blades composed of paddles 21-26 and 31-36 perpendicularly attached to the rotary shafts interposing gaps in the direction of the shaft and scrapers 41-46 and 51-56 attached to the tip ends of the paddles and having a length nearly corresponding to the dimension of the gaps. The stirring blade has an L/D ratio of 2-10, preferably 4-8 wherein D is rotary diameter of the blade and L is the length of the blade in longitudinal direction.

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 polyethylene terephthalate having a high degree of polymerization, and more particularly to a method for producing polyethylene terephthalate having a high degree of polymerization by a melt polymerization method.

[0002]

2. Description of the Related Art In a continuous production method of polyethylene terephthalate, a horizontal reactor of a uniaxial or biaxial stirring system has been conventionally used as a final polymerization machine. Among them, in order to obtain a polymer having a high degree of polymerization, the viscosity of the polymer is 10.
Since it will be more than 000 poise,
A biaxial stirring type as shown in No. 62620 is used.

4 and 5 show cross-sectional views of a conventionally used biaxial polymerization reactor. In the reactor shown in FIGS. 4 and 5, two rotating shafts 3 penetrate in parallel to the longitudinal direction of the reactor 1 having the jacket 2. A plurality of disc-shaped stirring blades 4 are fixed to the two rotating shafts 3 so as to overlap with each other, and the polymer is stirred by the rotation of the rotating shafts 3. Reference numeral 5 is a scraper provided on the outer peripheral side of the disk-shaped stirring blade.

The disk-shaped stirring blades 4 are adapted to rotate in mutually opposite directions (see FIG. 5). Further, a volatile matter exhaust nozzle 6 is provided above the reactor 1, and the volatile matter by-produced by the reaction is exhausted from the exhaust nozzle 6 to the outside of the system. An inlet 7 and an outlet 8 for the polymer are provided near both ends of the reactor 1 in the longitudinal direction. The intermediate polymer to be polymerized in the reactor 1 enters the reactor 1 through the polymer inlet 7 and is polymerized in the reactor 1 and discharged as the final polymer through the outlet nozzle 8.

Polymerization in the reactor 1 is carried out in several reactors.
The degree of vacuum is set to Torr or less, the temperature is 270 to 290 ° C., the disc-shaped stirring blade 4 is rotated to stir the polymer, and volatile gas such as reaction by-products is discharged from the discharge nozzle 6 to the outside of the system.

[0006]

The problem with the above-mentioned conventional apparatus is that the disc-shaped stirring blade 4 has two components as shown in FIG.
Since the blades are alternately attached to the rotary shaft 3 of the book and most of the blade side surface and the outer peripheral surface of the rotary shaft 3 are not self-cleaned, the flow is extremely deteriorated particularly on the blade side surface, which causes a dead space. The scraper 5 is mainly for scraping off the polymer on the inner wall of the reactor 1, and has a structure in which the adhering polymer on the side surface of the disk-shaped stirring blade 4 cannot be scraped off.

Still another problem is that there is a space between the inner wall of the reactor 1 and the upper part of the disk-shaped stirring blade 4 as seen in FIG. This space is provided for discharging the volatile component separated from the polymer through the exhaust nozzle 6, and is for keeping the pressure inside the reactor 1 uniform.

However, in this case, the polymer and the gas phase portion always have a gas-liquid interface. The portion A in FIG. 5 is the gas-liquid interface. This portion occurs over the entire length of the reactor 1 in the longitudinal direction. Poor flow also occurs at this gas-liquid interface, renewal of the adhered polymer is extremely deteriorated, and heat transfer (heating) from the jacket 2 is always performed, resulting in deterioration of the quality of the polymer due to retention for a long time. This deteriorated polymer is mixed in the product and causes deterioration of the quality of the product itself.

It is an object of the present invention to provide a production method capable of producing high quality polyethylene terephthalate having a high degree of polymerization by avoiding poor flow at the gas-liquid interface in the polymerization reaction.

[0010]

In order to solve the above-mentioned problems in the method for producing by continuous melt polycondensation of polyethylene terephthalate having a high degree of polymerization by an esterification reaction step and a polycondensation reaction step, the present invention provides: In the polycondensation reaction step, the intrinsic viscosity (η) measured in a mixed solvent at 20 ° C. in which the weight ratio of phenol and 1,1,2,2-tetrachloroethane is 4: 6 is 0.4 to 0. The pre-polycondensation step for obtaining polyethylene terephthalate of 9 dl / g and the poly (ethylene terephthalate) obtained in the pre-stage polycondensation step are subjected to polycondensation reaction as follows to obtain the above-mentioned intrinsic viscosity (η).
Of 0.8 to 1.3 dl / g is used to obtain polyethylene terephthalate.

That is, in the second-stage polycondensation step, a plurality of rotating shafts, a plurality of paddles attached to the rotating shafts at intervals substantially at right angles in the axial direction, and a tip portion of the paddles having the above-mentioned intervals.ゞ It has a stirring blade composed of a scraper having a corresponding length and mounted parallel to the rotating shaft, and the stirring blade has a structure of self-cleaning each other by its rotation, and the rotating diameter of the stirring blade is D In this step, the polycondensation reaction is carried out by using at least one stirring polymerization machine having an L / D expressed by the length L in the direction as L, which is 2 to 10, preferably 4 to 8. As a result, the drawbacks of the prior art can be solved, and a high quality polymer having an intrinsic viscosity of 0.8 to 1.3 dl / g can be obtained.

The characteristic feature of the method for producing a high degree of polymerization polyethylene terephthalate according to the present invention is that the polymerization having the above-mentioned structure having a complete self-cleaning function in the latter polycondensation step in which the viscosity of the polymer is high and the fluidity is apt to deteriorate. This is because the use of the reactor makes it possible to eliminate long-term accumulated substances in the reactor and obtain a polymer having a high degree of polymerization and good quality.

[0013]

The operation and action in the method for producing a high degree of polymerization polyethylene terephthalate according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a flow sheet in one embodiment of the continuous polymerization method of the present invention, 60 and 61 are esterification reaction tanks, 1 is a polymerization reactor showing a pre-stage polycondensation step, and the conventional one shown in FIGS. It is similar to the reactor used. Reference numeral 11 is a polymerization reactor showing a post-stage polycondensation step, the details of which are shown in FIGS. 2 and 3. 62, 63, 64
Is a transportation means for sequentially transporting the polymerized product to the next reactor.

The structure and operation of the polymerization reactor shown in the latter-stage polymerization step will be described in detail with reference to FIGS. 2 and 3. Figure 2
As shown in FIG. 3, in the reactor 11, two rotary shafts 12 and 13 are axially supported in parallel with each other, and each rotary shaft 12 and 13 is driven by a drive source (not shown) and indicated by an arrow in the drawing. Thus, they are rotationally driven in the same rotation direction and at the same rotation speed in synchronization with each other. The inner wall of the reactor 11 has a cocoon-shaped cross section in which two cylindrical walls 111 and 112 centering on the rotation shafts 12 and 13 are connected to each other. The rotary shafts 12 and 13 are round shafts 121 and 131, respectively.
And shaft covers 122, 1 having a pseudo-square cross section on the outer periphery thereof
32 (see FIG. 3).

A plurality of paddles 21, 22, 23, 24, 25, 26 are fixed to the rotary shaft 12 at a predetermined interval. Each of the paddles 21 to 26 is formed in a thick plate shape having a spindle-shaped cross section in which the central portion swells and both ends are sharp,
The paddles 21 to 26 are attached to the rotary shaft 12 along a plane orthogonal to the paddles 21 to 26, and the adjacent paddles 21 to 26 arranged side by side in the axial direction of the rotary shaft 12 are out of phase with each other by 90 degrees. It is in a state of Further, the tips of the paddles 21 to 26 are dimensioned so that they can face the cylindrical wall 111 of the reactor 11 or the corresponding paddles 31 to 36 described later with a slight clearance depending on the rotational angular position. Has been selected.

On the other hand, also on the rotary shaft 13, a plurality of paddles 31, 32, 33, 34, 35, 36 having a spindle-shaped cross section are similarly provided.
Has been fixed. The paddles 31 to 36 are located at the same axial positions as the paddles 21 to 26, respectively, and are attached to the rotary shaft 13 with their phases shifted by 90 degrees with respect to the corresponding paddles 21 to 26. Has been. Further, the tips of the paddles 31 to 36 are separated from each other by a slight clearance according to the rotational angle position of the reactor 11 and
Cylindrical wall 112 or corresponding paddles 21-26, respectively
To be able to face.

Further, scrapers 41 to 46, 51 to 56 having a solid triangular cross-section corresponding to the cross-sectional shape of the tips of the paddles 21 to 26, 31 to 36 are parallel to the rotary shafts 12 and 13, respectively. It is fixed to. The tip surfaces of the scrapers 41 to 46, 51 to 56 face the adjacent paddles 21 to 26, 31 to 36 with a slight clearance in the axial direction.

Since the scrapers 41 to 46 and 51 to 56 have the same structure, the scraper of the paddle 23 will now be described in detail as a representative. The tip ends of the scrapers 43 are arranged so as to closely face the side surfaces of the paddles 32 and 34 and face each other. Each scraper 43
Of the scraper 43 is located on the same line as the corresponding tip of the scraper 43, so that the tip of each scraper 43 has a slight clearance depending on the rotational angle position of the rotary shaft 12 and the cylindrical wall of the reactor 11. 111 or paddle 33
May be opposed to the shaft cover 132 having a surface continuous with the.

Further, as shown in FIG.
The scrapers 52 and 54 attached to the adjacent paddles 32 and 34 are inserted between the shaft cover 122 and the shaft cover 122 in accordance with the rotation, and when these are inserted, the scraper 43 is surrounded by the shaft center side. Face and scraper 5
The dimensions are selected so that the peripheral surfaces of the shafts 2, 54 are closer to each other with a slight clearance. The paddle and scraper having the above structure constitute the stirring blade according to the present invention.

In such a polymerization reactor, the polymerized product is introduced into the reactor 11 through the inlet 201, the rotating shaft 12,
The paddles 21 to 26, 31 to 3 are driven and rotated by 13
6 and the scrapers 41 to 46, 51 to 56 are stirred by the stirring action, and then taken out from the outlet 202. Here, as can be seen from the sectional view of FIG.
2, 13 and the scrapers 41 to 46, 51 to 56 occupy a small volume, and the paddles 21 to 26, 31 to 36 are also attached at intervals, so that the effective volume ratio in the reactor 11 can be adjusted by the conventional self It can be greatly increased as compared with a cleaning type stirring device.

In the illustrated example, the effective volume is 7 of the total volume.
It is 0 to 75%. If necessary, paddle 2
The effective volume ratio can be further increased by expanding the mounting intervals of 1 to 26 and 31 to 36 and lengthening the lengths of the scrapers 41 to 46 and 51 to 56 accordingly. on the other hand,
At the same time as the stirring action, the following cleaning action causes each part in the reactor 11 to be self-cleaned.

That is, the inner wall of the reactor 11 is the paddle 2
1-26, 31-36 tips, and scrapers 41-4
Cleaning is performed by moving the tip traverse portions of 6, 51 to 56 close to each other. Further, the curved peripheral surfaces of the paddles 21 to 26 and the paddles 31 to 36 are cleaned by moving their tips close to each other.

Further, the plane side surfaces of the paddles 21 to 26, 31 to 36 and the scrapers 51 to each facing them.
The tip surfaces of 56, 41 to 46 are moved close to each other to be cleaned. For example, paddle 2
The planar side surface of 2 moves relatively close to the tip surfaces of the scrapers 51 and 53, and the opposing surfaces thereof are cleaned.

The scrapers 41 to 46, 51 to 56
The peripheral surfaces are cleaned by moving the scrapers 41 to 46, 51 to 56 with their tips and the peripheral surface moved close to each other. Thus, the relative movement of the paddles 21 to 26, 31 to 36 and the scrapers 41 to 46, 51 to 56 by the rotation of the rotating shafts 12 and 13 can completely clean all the surfaces in the container 11.

In order to sharpen the distribution of the degree of polymerization of the polymer (final polymerized product) at the reactor outlet 202, generally, the retention time distribution of the treated material in the reactor 11 (= the average retention time) It is important to make the variation) uniform. To this end, the diameter of the stirring blade (D)
It is necessary to increase the ratio L / D of the length (L) in the axial direction to the axial direction or to suppress the mixing in the axial direction as much as possible by installing a partition plate or the like in the axial direction in the reactor 11.

When a polyethylene terephthalate having a high degree of polymerization is polymerized, the viscosity is high (about 10,000 to 30,000 Poise), and L / D = 2 to 10, preferably about 4 to 8 for partitioning. Even without a plate, a good retention time distribution can be obtained.

Although two rotary shafts are provided in the above example, the present invention is not limited to two, and three or more rotary shafts can be provided. Further, in the above-mentioned example, the scraper has a solid triangle cross section, but it may have a columnar shape or a columnar shape.

[0028]

EXAMPLES Examples of the method for producing polyethylene terephthalate having a high degree of polymerization according to the present invention will be specifically described below.

Example 1 Using the apparatus shown in FIG. 1, 1.0 mol of terephthalic acid and 1.
The raw material slurry mixed at a rate of 5 mol was continuously supplied to the first stage esterification tank at a rate of 6 kg per hour. In this slurry, antimony trioxide as a catalyst and triphenyl phosphate as a stabilizer were added to the raw material slurry at a ratio of 350 ppm and 300 ppm, respectively. The esterification reaction was performed in the esterification reaction tanks of the first and second stages up to a reaction rate of about 96%. At this time, the conditions of the first and second stage esterification reaction tanks were that the temperature was 260 ° C. and the retention time was 4.5 hours and 2 hours, respectively.

Next, the prepolymer was treated at a temperature of 270 ° C.
The pressure was controlled to 2 Torr. The biaxial horizontal stirring type pre-stage polymerizer shown in FIG. 5 (L / D = 4, stirring blade rotating diameter 16
6 mm, internal volume 18 liters, stirring speed 20 rpm),
It was pushed in by a gear pump at the outlet of the second stage esterification tank, and the polymerization was carried out for a retention time of about 2 hours. The intrinsic viscosity (η) of the obtained polymer was 0.64 dl / g.

Next, this polymer was controlled at a temperature of 275 ° C. and a pressure of 0.3 Torr, and the biaxial horizontal stirring type post-polymerization unit (L) having a self-cleaning function shown in FIG.
/ D = 6, stirring blade rotation diameter 100 mm, internal volume 6 liters, stirring rotation number 30 rpm) was pushed by the gear pump 64 at the exit of the preceding-stage polymerization unit, and polymerization was carried out for 40 minutes in retention time.
The intrinsic viscosity (η) of the obtained polymer was 1.12 dl / g. Other test results are shown in Table 1.

Example 2 In the latter-stage polymerization reactor of Example 1, the same polymerization as in Example 1 was carried out except that the pressure was 0.1 Torr, and the obtained polymer was analyzed in the same manner. The results are shown in Table 1.

Example 3 The same analysis as in Example 1 was conducted on the polymer obtained by carrying out the same polymerization as in Example 1 except that the pressure in the post-polymerization vessel was changed to 1.0 Torr. The results are shown in Table 1.

(Example 4) In Example 1, one part of the polymer to be sent to the post-stage polymerization vessel was continuously extracted from the gear pump 64 at the outlet of the pre-stage polymerization vessel to the outside of the system to reduce the amount of the polymer to be sent to the post-stage polymerization vessel, and the post-stage polymerization The same analysis was performed on the polymer obtained by performing the same polymerization as in Example 1 except that the retention time in the vessel was set to 60 minutes. The results are shown in Table 1.

(Comparative Example) Example 1 was repeated except that the type of the second-stage polymerizer was the same as that of the former-stage polymerizer (however, the internal volume was 10 liters) and the retention time was 60 minutes. The same polymerization as in Example 1 was performed, and the obtained polymer was analyzed in the same manner. The results are shown in Table 1.

[0036]

[Table 1]

[0037]

According to the present invention, after the esterification step in which a mixture of terephthalic acid and ethylene glycol is subjected to an esterification reaction, the prepolymer obtained in this esterification step is subjected to a polycondensation reaction to obtain an intrinsic viscosity ( η) is 0.4 ~
A pre-stage polycondensation step for obtaining polyethylene terephthalate of 0.9 dl / g, and a specific biaxial horizontal stirring type polymerization having a self-cleaning mechanism for further increasing the degree of polymerization of the polyethylene terephthalate obtained in this pre-stage polycondensation step The polycondensation reaction is performed in a vessel and the intrinsic viscosity (η) is 0.8-
Since polyethylene terephthalate is produced through a post-stage polycondensation step for obtaining polyethylene terephthalate of 1.3 dl / g, polyethylene terephthalate having a high degree of polymerization and excellent quality can be obtained.

[Brief description of drawings]

FIG. 1 is a process drawing showing the flow of polyethylene terephthalate production in one embodiment of the present invention.

FIG. 2 is a sectional view of the latter-stage polycondensation reactor in FIG.

FIG. 3 is a sectional view taken along line 11-11 in FIG.

FIG. 4 is a cross-sectional view of a conventionally used biaxial polymerization reactor.

5 is a sectional view taken along line I-I in FIG.

[Explanation of symbols]

 1 1st-stage polymerization reactor 11 2nd-stage polymerization reactor 12,13 Rotating shaft 21-26 Paddle 31-36 Paddle 41-46 Scraper 51-56 Scraper 60,61 Esterification reaction tank 111,112 Cylindrical wall 122,132 Shaft cover

Claims (1)

[Claims] 1. A method for producing polyethylene terephthalate having a high degree of polymerization by continuous melt polycondensation in an esterification reaction step and a polycondensation reaction step, wherein the polycondensation reaction step comprises phenol, 1, 1, 2, A pre-stage polycondensation step for obtaining polyethylene terephthalate having an intrinsic viscosity (η) of 0.4 to 0.9 dl / g measured in a mixed solvent of 20 ° C. in which the weight ratio of 2, -tetrachloroethane is 4: 6; The polyethylene terephthalate obtained in the pre-stage polycondensation step is provided with a plurality of rotating shafts, a plurality of paddles axially attached to the rotating shafts at intervals substantially at right angles, and a tip portion of the paddles having the intervals.ゞ a stirring blade made of a scraper having a corresponding length and mounted parallel to the rotating shaft, and the stirring blades have a structure of self-cleaning each other by the rotation thereof. L / D, where L is the rotational diameter of the impeller and L is the axial mounting length of the impeller, is 2 to 10, preferably 4 to 8, and is supplied to at least one stirring polymerization machine to perform polycondensation. After the reaction, the above-mentioned intrinsic viscosity (η) is 0.8.
A method for producing a high degree of polymerization polyethylene terephthalate, which comprises a post-polycondensation step for obtaining polyethylene terephthalate of 1.3 dl / g.