JPH0236229A - Apparatus for continuous polymerization of polycapramide - Google Patents

Abstract

PURPOSE:To obtain a polycapramide having excellent quality by spraying water into a mixture of prepolymer vapor and steam at the top of a continuous polymerization column for caprolactam to effect the partial condensation of the prepolymer vapor and the control of the internal pressure. CONSTITUTION:A prepolymer produced by the prepolymerization of epsilon- caprolactam is supplied to a continuous polymerization column to obtain a polycapramide. In the above process, water is sprayed to a mixture of steam and prepolymer vapor at the top 1 of the continuous polymerization column to effect the partial condensation of the prepolymer vapor and, at the same time, steam is condensed at the top 1 of the continuous polymerization column and the internal pressure at the top 1 is controlled. A polycapramide having low fluctuation of viscosity and high quality can be produced by this process.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a continuous polymerization apparatus for polycapramide, and in particular a VK tower (Verei
The present invention relates to a continuous polymerization apparatus for polycapramide, which is capable of effectively advancing continuous polymerization of polycapramide by efficiently separating e-caprolactam initial polymerization vapor and water vapor in a reactor.

[Prior Art] The following method is known as one method for continuously producing polycapramide. That is, water is added to ε-caprolactam as a polymerization initiator and heated to perform initial polymerization, and the mixed vapor of the generated initial polymer vapor (including 1,000 yen) and water vapor is converted into VK tower C, which is simply referred to as a tower. be)
This is a method in which continuous polymerization is carried out by sending the polymer to in this way,
Polymerization of the initial polymer proceeds as the mixed vapor rises from the bottom of the column to the top of the column heated to about 220°C to 270°C. The produced polycapramide polymer then flows down to the bottom of the column. However, the initial polymer and unreacted monomers (hereinafter sometimes referred to as initial polymer) whose polymerization is not promoted rise in a mixed state with water vapor and reach the top of the column. Among the mixed vapor at the top of the column, high-boiling point initial polymers are condensed by partial condensation, come into contact with the mixed vapor rising from the bottom of the column, polymerize, and flow down. On the other hand, the steam separated at the top of the column is discharged from the top of the column.

In such a method, the mixed vapor at the top of the tower can be separated by installing a multi-tube cooler in the gas phase at the top of the tower (Japanese Patent Publication No. 39-12304) or by reducing the pressure in the gas phase at the top of the tower. A method of separating ε-caprolactam by flowing the ε-caprolactam melt against the wall surface of the gas phase to prevent monomers and foreign substances from sticking to the wall surface (Japanese Patent Application Laid-Open No. 51-144
493) is known.

[Problem to be solved by the invention] However, in the former method using a multi-tubular cooler, when the amount of mixed vapor in the gas phase at the top of the tower fluctuates, it is difficult to immediately adjust the temperature in response to the fluctuation. However, there was a problem in that the temperature easily fluctuated. Fluctuations in temperature lead to fluctuations in the gas phase pressure, and as a result, the moisture content of the condensate changes, causing viscosity unevenness in the polycapramide product and degrading its quality. There was also the risk that monomers and foreign matter would adhere to the cooler, reducing thermal efficiency.

On the other hand, in the case of the latter method, in which the pressure is reduced in the gas phase, the level of polymer at the top of the tower fluctuates greatly due to the pressure reduction, and as in the former case, there is the problem that the amount of water brought in, such as the initial polymer, fluctuates. Ta.

The present invention was made under these circumstances, and even when the amount of mixed vapor in the top gas phase varies, it does not cause temperature fluctuations and has a high quality with less viscosity unevenness. The object of the present invention is to provide a continuous polycapramide polymerization apparatus capable of obtaining a product polymer.

[Means for Solving the Problems] The present invention provides an apparatus for initially polymerizing ε-caprolactam and sending the initial polymerized product to a continuous polymerization tower to obtain polycapramide. A mechanism for partial condensation of the initial polymer vapor by injecting water is provided, and a mechanism for condensing water vapor and adjusting the internal pressure at the top of the continuous polymerization column is attached to the top of the continuous polymerization column. This is a summary.

[Function] The present inventors have established a method that can quickly respond to changes in the amount of mixed steam without delaying temperature adjustment when partial condensing the mixed steam in the gas phase at the top of the tower. I considered it carefully.

As a result, instead of using a multi-tubular cooler, the present invention was completed based on the idea of spraying water directly onto the mixed steam from above in the gas phase at the top of the tower. That is, when water is directly sprayed, the steam is directly cooled, so even if the amount of mixed steam changes, it can be quickly dealt with by changing the amount of water sprayed. Therefore, initial polymerization products of high-boiling components can be efficiently condensed without causing temperature fluctuations.

FIG. 1 is a schematic cross-sectional view illustrating the continuous polymerization apparatus of the present invention, in which 1 is the top gas phase, 2 is the water pipe 23 is the spray nozzle, 4 is the exhaust steam line, 5 is the packed bed, and 6 is the mixed steam population.

A mixed vapor of water vapor and an initial polymer obtained in advance by adding water to ε-caprolactam and heating and polymerizing the mixture is introduced into the column from the vapor population 6. The mixed steam and water come into contact with each other while rising inside the packed bed 5. The mixed steam that has reached the top gas phase 1 is cooled by water sprayed from a spray nozzle 4 attached to the tip of the water pipe 2. As a result, the mixed vapor is fractionated, and the condensate rich in high-boiling components such as initial polymers is refluxed to the packed bed 5, where it comes into contact with the mixed gas rising from below the packed bed, and the high-boiling components are removed from the column. taken out from the bottom. On the other hand, the low-boiling components rich in water vapor in the mixed vapor at the top of the tower are introduced into the total condenser shown in FIG. 2 (schematic cross-sectional diagram) through the exhaust steam line 4 without being condensed.

In Fig. 2, 11 is a tube type total condenser, 12 is an exhaust steam introduction pipe connected to the exhaust steam line 4 of the VK tower, 13 is a cold water introduction pipe, 14 is a cold water discharge pipe, 15 is a tube, and 16 is condensed water. An inlet pipe, 17 a water seal tank, 18 a pressure regulator, and 19 a drainage line.

Exhaust steam discharged from the exhaust steam introduction pipe 12 is introduced into the tube type total condenser 11. The condensed liquid is then condensed by exchanging heat with the cold water in the tube 15.
7. In addition, when the amount of steam in the gas phase at the top of the tower fluctuates, an internal pressure detector (not shown) installed in the tower sends a signal to the pressure regulator 18 installed in the water seal tank 17. As a result, the water head in the water seal tank 17 is adjusted by the pressure regulator 18, and the pressure in the gas phase at the top of the tower is adjusted.

In FIG. 2, a tube type full condenser 11 is used, but the full condenser used in the present invention is not limited to a tube type, and has the function of fully condensing exhaust steam. As long as it is a product, its structure, format, and type do not matter.

Examples will be described below, but the present invention is not limited to the following examples, and it is within the technical scope of the present invention to make appropriate design changes in keeping with the main idea described above and below.

[Example] Continuous polymerization tower of the present invention using a 5% water-containing ε-caprolactam aqueous solution as a raw material for polycapramide and a conventional continuous polymerization tower in which a multi-tubular warm water Mi vessel was installed at the top of the VK tower for comparison. Continuous polymerization was carried out using the following methods.

The design conditions of the device were as follows.

The supply rate of mixed steam to the VK tower was 347 g/
It was a minute.

When we investigated the temperature variations in the top gas phase (partial condensation part) and the variations in the viscosity of the polymer at the exit of the polymerization tower, we obtained the following results.

As is clear from the above results, the variation in temperature of the gas phase part (partial condensation part) in the example of the present invention was smaller than that in the conventional example, and therefore the variation in the viscosity of the polymer was also extremely small.

[Effects of the Invention] Since the present invention is configured as described above, temperature fluctuations and pressure fluctuations in the VK tower top gas phase region are not caused. Therefore, it has become possible to provide a continuous polymerization apparatus that can produce polycapramide of good quality with little variation in viscosity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a continuous polymerization column according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a total condenser attached to the top of the continuous polymerization column in FIG. 1... Tower top gas phase section 2... Water pipe 3... Spray nozzle 4... Exhaust steam line 5... Packed bed
6...Mixed steam population 11...Tube type total condenser 12...Exhaust steam introduction pipe 14...Cold water discharge pipe 16...Condensed water introduction pipe 18...Pressure regulator 13... Cold water introduction pipe 15...tube 17...water seal tank 19...drainage line

Claims (1)

[Claims] (1) In an apparatus for initially polymerizing ε-caprolactam and sending the initial polymerized product to a continuous polymerization tower to obtain polycapramide,
A mechanism for condensing the initial polymer vapor by injecting water into the water vapor-initial polymer vapor mixture at the top of the continuous polymerization column is provided, and a mechanism is provided at the top of the continuous polymerization column for condensing water vapor and for condensing water vapor at the top of the continuous polymerization column. A continuous polymerization device for polycapramide, characterized in that it is equipped with a mechanism that can adjust the internal pressure of the polycapramide.