JPH0678435B2 - Method and apparatus for continuous solid-state polycondensation of thermoplastic resin - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a continuous solid-phase polycondensation method and apparatus for thermoplastic resins such as granular polyethylene terephthalate and polypropylene terephthalate.

[Background of the Invention]

A conventional solid phase polycondensation method for thermoplastic resins is disclosed in JP-A-56-11.
As described in Japanese Patent No. 2925, an inert gas containing ethylene glycol is passed through a solid-state polymerization reactor and impurities such as acetaldehyde and ethylene glycol mixed in the inert gas are introduced into an adsorption tower to be adsorbed and removed. As a result, the inert gas is recycled. in this case,
The impurities contained in the inert gas also include a gas having a small adsorbing effect by the adsorbent, and these remain in the inert gas and cause deterioration of product quality. Also, the adsorption tower is used by periodically switching between adsorption and desorption.
The adsorbent is regenerated during desorption. The lower the inert gas temperature of the adsorbent, the better the adsorption performance, but in order to lower the temperature of the inert gas introduced into the adsorption tower, it is necessary to cool the inert gas discharged from the solid polycondensation reactor. The heat exchanger becomes large. Further, since a lot of equipments such as the adsorption tower switching equipment and the heat exchanger auxiliary equipment are required, the equipment cost becomes high and the operation becomes complicated.

[Object of the Invention]

An object of the present invention is to provide a continuous solid-phase polycondensation method and apparatus for a thermoplastic resin, which has a simple facility and can efficiently obtain a high-quality thermoplastic resin containing few thermally decomposable impurities.

[Outline of Invention]

In the present invention, a granular thermoplastic resin is preheated in the reactor and then heated to a temperature close to the melting point to carry out a solid-phase polycondensation reaction under reduced pressure, and at the same time, the generated thermally decomposable impurities are removed in the reactor. By discharging the exhaust gas together with the exhaust gas, a high-quality thermoplastic resin containing few impurities can be continuously obtained with simple equipment.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. In the figure, 1 is a vertical cylindrical reactor body having a solid granular raw material inlet 2 at the upper portion and a granular product outlet 3 at the lower portion, 4, 5,
Reference numeral 6 denotes a jacket which is attached to the outer periphery of the reactor body 1 in three parts in the longitudinal direction, and in the jacket 4, a preheating section A for preheating the granular resin supplied by circulating steam as a heat medium is constituted. The jacket 3 is provided with a reaction part B in which a heat medium of a different kind or the same kind, for example, oil is circulated to raise the temperature of the preheated granular resin to a predetermined temperature near the melting point, and hot water is circulated in the jacket 6, for example. A cooling unit C for cooling the product after the reaction. Reference numeral 7 denotes an exhaust tube in which the outer circumference of a perforated cylinder provided in the reaction section in the reactor body 1 is surrounded by a net of about 20 mesh, and is connected to a vacuum exhaust device (not shown) via an exhaust pipe 8. . Reference numeral 9 denotes a discharge device provided with a stirring blade provided on the product outlet 3 side in the reactor main body 1, which is supported by a bearing 10 and driven by an electric motor 11. 12 is a raw material supply hopper for continuously supplying raw material from the granular raw material inlet 2 into the reactor main body 1 through a continuous supply valve 13 having a sealing function, and 14 and 15 are cooling provided on the product outlet 3 side. It is a continuous exhaust valve having a container and a sealing function. The ratio of the length (height) to the inner diameter of the reactor is not particularly limited, but is generally 3:
It is from 1 to 30: 1, preferably from 5: 1 to 20: 1.

In the above-mentioned configuration, while the inside of the reactor main body 1 is kept in high vacuum by the exhaust pipe 7, the raw material is continuously supplied from the raw material supply hopper 12 through the continuous supply valve 13 through the raw material inlet 2 into the reactor main body 1. The granular raw material is buried in the reactor, and while being discharged from the lower part, it naturally descends in the reactor, is preheated in the preheating section A, and is then heated in the reaction section B to a predetermined temperature near the melting point. The temperature is raised to carry out a solid-phase polycondensation reaction, the product is cooled in the cooling section C, taken out from the product outlet 3 by the discharging device 9, cooled to room temperature in the cooler 14 and discharged as a product from the continuous discharging valve 15. . In this case, impurities generated by thermal decomposition due to the polycondensation reaction in the reaction section B are discharged together with the exhaust gas from the exhaust stack 7, and thus do not remain in the product.

The degree of polymerization can be increased to a desired value by appropriately setting the residence time and temperature in the reactor, especially in the reaction section B.

At this time, the average residence time is determined by adjusting the feed rate and the discharge rate.

Also, in order to keep the degree of polymerization of the discharged product particles uniform, avoid a short path in the reactor if necessary,
A guide plate or the like may be appropriately provided in order to keep the residence time substantially constant.

Further, the temperature is set to a desired temperature according to the temperature of the heat medium of the jacket of the corresponding portion.

In order to make the temperature uniform, a gentle stirring mechanism may be added so as to move the particles in the horizontal direction.

〔Example〕

Continuously using granular polystyrene terephthalate with IV value of 0.8
It is supplied from the top into the reactor body 1 held at 0.1 mmHg, preheated to 100-150 ° C in the preheating section A, and about 200 in the reaction section B.
After raising the temperature to ℃ and setting the passage time for this part to be about 5 hours to carry out the solid-phase polycondensation reaction, the generated heat-decomposable impurities are removed and then cooled to about 50 ℃ in the cooling part C. Take out from the reactor body 1 and cool to room temperature with the cooler 14 to obtain IV value
A high-purity product of 1.0 was obtained.

〔The invention's effect〕

As described above, according to the present invention, when a solid thermoplastic resin is preheated in a reactor and then heated to a temperature close to the melting point, and retained for a predetermined reaction time to carry out a solid phase polycondensation reaction under reduced pressure. At the same time, the heat-decomposable impurities generated are discharged together with the exhaust gas in the reactor so that solid-phase polymerization is continuously carried out.Therefore, the heat exchanger and the adsorption tower in the prior art and the auxiliary equipment thereof are required. In addition, the reactor itself can be downsized, and a continuous solid-state polycondensation method and apparatus for a thermoplastic resin capable of obtaining a high-quality product with simple equipment can be provided.

[Brief description of drawings]

The drawing is a longitudinal sectional view of a continuous solid-state polycondensation apparatus for thermoplastic resins, showing an embodiment of the present invention. 1 ... Reactor body, 2 ... Raw material inlet, 3 ... Product outlet,
4,5,6 ... Jacket, 7 ... Exhaust stack, 8 ... Exhaust pipe,
9 ... Discharge device, 10 ... Bearing, 11 ... Electric motor, 12 ... Raw material supply hopper, 13 ... Continuous supply valve, 14 ... Cooler,
15 ... Continuous discharge valve, A ... Preheating section, B ... Reaction section, C ...
… Cooling unit

Claims (2)

[Claims] 1. A vertical cylindrical reactor having a granular thermoplastic resin supply port on an upper part, a discharge port on a lower part, a heating jacket on at least a side surface thereof, and an exhaust hole inside thereof is used. The granular solid thermoplastic resin is supplied from the upper supply port and discharged from the lower discharge port, while the granular resin is buried inside and continuously descends from the upper part to the lower part,
A continuous solid phase of a granular thermoplastic resin characterized in that it stays in the reactor for a predetermined time, is heat-treated at a predetermined temperature in each part, and sequentially performs a preheat polymerization reaction from the upper part, and discharges polymerization reaction completed particles from the lower part. Polymerization method. 2. A vertical cylindrical reactor main body having a raw material inlet provided with a continuous supply valve having a sealing function at an upper portion and a product outlet provided with a continuous discharge valve having a sealing function at a lower portion. A preheating section, a reaction section, and a cooling section are formed in the reactor body by providing a jacket on the outer periphery, which is divided into three parts in the longitudinal direction and through which heat media having different temperatures flow, and an exhaust pipe is provided in the reaction section in the reactor body. A continuous solid-state polycondensation device for a thermoplastic resin, characterized in that an exhaust tube connected to a vacuum exhaust device via a vacuum exhaust device is provided, and an exhaust device is provided on the lower product outlet side of the reactor body.