JPS59196301A - Separation of olefin polymer - Google Patents

Abstract

PURPOSE:To reduce the thermal load of a separation tank, to prevent the clogging of heating tube, and to separate polymer powder effectively, by feeding an olefin polymer to a heating tube maintained at a predetermined temperature before feedigng the olefin polymer from a reaction tank or the like to a separation tank. CONSTITUTION:An olefin polymer (e.g., polyethylene or polypropylene) suspension discharged from a reaction tank or a washing tank 1 is fed to a heating tube 3 and at the same time the temperature of the suspension at the exit 4 of the heating tube 3 is maintained at a temperature of (Tb+55 deg.C) or below, preferably at a temperature of (Tb+40 deg.C)-(Tb+50 deg.C) wherein Tb is the boiling pont of the suspension in the heating tube 3. The suspension is then fed to a separation tank, where the olefin polymer powder is separated from unreacted monomer, an inert hydrocarbon, etc. In this way, the purpose olefin polymer powder can be separated and recovered efficiently in good yeild.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating olefin polymers, and more specifically, a method for reducing the heat load on a separation tank by introducing the olefin polymer into a heating tube maintained at a constant temperature before introducing the olefin polymer into the separation tank. The present invention relates to a method for efficiently separating olefin polymers by reducing the amount of water and preventing clogging of heating tubes.

Conventionally, in the production of olefin polymers such as polyethylene and polypropylene, a method for separating diolefin polymers from a suspension of products containing monomers, etc.
From a relatively high-pressure reaction tank or washing tank to normal pressure or reduced pressure via an intermittent operation valve! ! In order to reduce the heat load on the cypress, a heating tube is usually installed before the separation tank to perform preheating. For example, in the case of bulk polymerization of propylene, separation is performed after preheating at 20 to 30°C and 9/ff1G to Ω~1 (Japanese Patent Application Laid-Open No. 1983-1979-1).
145091). However, if preheating is carried out at a relatively high temperature of 20 to 30°C or more, the suspension medium such as monomers will evaporate and the suspension will not lose its fluidity. Alternatively, a problem arises in that a small amount of amorphous polymer or the like contained in the IC precipitates and causes blockage. Such clogging of the heating tube not only makes continuous operation impossible, but also poses an extremely high risk for work.

Therefore, the present inventors investigated a method for efficiently separating an olefin polymer without clogging the heating tube, and as a result, completed the present invention. The present invention will be explained as follows based on the drawings. .

That is, the present invention provides a method in which a suspension of an olefin polymer discharged from a reaction tank or a cleaning tank 1 is introduced into a heating tube 3, and then the olefin polymer is separated in a separation tank 5. The temperature of the suspension at (Tb+5
s°C) or less (Tb: boiling point of the suspension in the heating tube). ) is provided.

The olefin polymer to which the separation method of the present invention is applied is not particularly limited, and specifically, polyethylene, zaribrobylene,
Polybutene-1. ethylene-α-olefin copolymer,
Examples include propylene-α-olefin copolymers. The olefin polymer suspension obtained by the polymerization reaction contains a polymer, an inert solvent, and a reaction medium (unreacted monomer).

Contains oligomers or amorphous rimers, etc.
It is necessary to separate these from the desired olefin polymer.

There are no particular restrictions on the polymerization method used to produce the above olefin polymer; for example, pallid polymerization may be used.

Although various methods such as slurry polymerization and solution polymerization can be applied, bulk polymerization and slurry polymerization are particularly suitable in the present invention.

The conditions for polymerization are not particularly limited and may be determined as appropriate depending on the type of monomer used, the polymerization type, or the required characteristics of the olefin polymer to be produced. However, in the case of propylene polymerization, the reaction In the tank, the reaction temperature is 60-100°C, r+ or 50-80°C, the reaction pressure is 20-451°, preferably 25-4'Okg/
It is carried out under cria conditions. The reaction mixture containing the olefin polymer produced by this polymerization reaction, that is, the suspension of the olefin polymer, is washed as necessary, but is usually kept in a washing tank at a temperature of 20 to 75°C.
°C, preferably 40 to 70 °C, pressure 15 to 40 kg/c
dG1 The suspension containing the olefin polymer introduced from the reaction tank under the conditions of preferably 20 to 30 Y/da is washed with an inert hydrocarbon such as penmen, hexane, hebukun, etc. or with the olefin monomer itself. In the case of slurry polymerization of polyethylene, it is usually carried out at a temperature of 20 to 500°C, preferably 50 to 180°C, and a pressure of 1 to 70°C/d.

In the method of the present invention, the above-mentioned suspension is directly introduced from the reaction tank into the heating tube 3, or the suspension is added from the reaction tank via a washing tank. This can be applied to any case where the above suspension is introduced into the tube 3.

According to the method of the present invention, the olefin polymer suspension in the reaction tank or washing tank 1 is first heated in the heating pipe 3 by continuously opening and closing the valve 2 intermittently or continuously. After being preheated, it is led to a separation tank 5 via a heating tube outlet 4, where the olefin polymer is separated.

Generally, the reaction tank or cleaning tank 1 is under high pressure of several tens of atmospheres, while the inside of the heating tube 5 and separation tank 5 is under reduced pressure or normal pressure of about 0.2 to 2 atmospheres. As a result, the suspension led from the reaction tank or cleaning tank 1 to the heating tube 3 or separation tank 5 is flashed and its temperature drops rapidly. Therefore, if the suspension is directly led from the reaction tank or the washing tank 1 to the separation tank 5, the thermal load on the separation tank 5 will be extremely large, causing various problems. Therefore, it is necessary to once introduce the suspension from the reaction tank or washing tank 1 to the heating tube B and preheat it. However, if the preheating temperature in the heating tube 3 is too high, media such as monomers and inert hydrocarbons in the suspension will excessively evaporate and escape, resulting in heating by the remaining polymer and/or amorphous polymer, etc. There is a risk that the tube 3 will become blocked.

Therefore, in the method of the present invention, the temperature of the suspension at the outlet 4 of the heating tube 5 is maintained at below (Tb+s5)"c, preferably in the range of (Tb-)40) to (Tb-)50)C. Here, at low temperatures below (Tb + 40) °C, the heat load on the separation tank 5 increases and the significance of preheating is lost. On the other hand, at low temperatures exceeding (Tb + 55) °C, as mentioned above, It is not preferable that olefin polymers, amorphous polymers, etc. adhere or precipitate and block the heating W5.

Although there are various methods for heating w5, a method in which a heating medium such as steam is passed through the outside of the heating tube 5 is usually adopted.

In the method of the invention, the suspension thus preheated is discharged from the outlet 4 of the heating tube 6 and introduced into the separation tank 5. Here, the olefin polymer powder and unreacted monomer,
Inert hydrocarbons are separated, and the desired olefin polymer powder can be efficiently separated and recovered with high purity. Note that the operating conditions in the separation tank 5 at this time are as follows:
Although there are no particular limitations, the temperature is preferably below the temperature at which the polymer does not deteriorate due to heat, preferably below the melting temperature.

According to the method of the present invention, suspensions in which the concentration of solid matter is 15 to 60% by weight as the olefin polymer powder and 5% by weight as the amorphous polymer can be efficiently separated. can.

As described above, according to the present invention, the olefin polymer can be efficiently separated from other impurities without clogging the heating tube, and is extremely useful in the production of olefin polymers.

Next, the present invention will be explained in detail using examples.

Examples 1 to 3 and Comparative Examples 1 to 5 A suspension obtained by bulk polymerizing propylene at 70°C and a pressure of 3sky/c++ [o] was placed in reaction tank 1 with an inner diameter of 2.7cm.

1.5 kl on the outside with a double pipe with a length of ion? /cnIG
The mixture was introduced into a heating tube B heated with steam at 110°C while adjusting the supply amount so that the temperature at the outlet 4 would be the value shown in Table 1 by intermittently opening and closing the valve 2. The suspension momentarily passed through the heating tube 3 when the valve 2 was opened.

The suspension that has passed through the heating tube 3 has a temperature of 80°C, a pressure of 0, (
The polypropylene powder was separated from the other components. The results are shown in Table 1.

Examples 4, 5 and Comparative Examples 4, 5 Ethylene at 80°C, 45.5 kl? The procedure of Examples 1 to 5 was repeated except that the slurry polymerization was carried out in isobutane under the conditions of /cIiG. The results are shown in Table 2.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the apparatus from the reaction tank or washing tank to the tank M. 1... Reaction tank or cleaning tank, 2... Valve, 3... Heating tube. 4... Heating tube outlet, 5... Separation tank Patent applicant Idemitsu Petrochemical Co., Ltd.

Claims (1)

[Claims] The olefin polymer suspension discharged from the reaction tank or washing tank (1) is introduced into the heating tube (3), and then into the separation tank (
In the method for separating the olefin polymer in step 5), the temperature of the suspension at the outlet (4) of the heating tube (3) is set to (Tb+
55℃) or below (TI): The boiling point of the suspension in the heating tube (°
C) is shown. ) A method for separating an olefin polymer, characterized by maintaining the same.