JPH04170401A - Method for drying polybutadiene rubber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to the desolvation of a polybutadiene solution obtained by polymerizing 1,3-butadiene in a polymerization solvent consisting of a C1 fraction containing cis-2-butene as a main component. , concerning the purification of polybutadiene.

[Conventional technology and issues]

Generally, desolvation methods for recovering rubber from a rubber solution include steam stripping and a desolvation method using a vent extruder.

The steam stripping method releases a rubber solution into water;
The rubber is coagulated and recovered as crumbs, then dehydrated and pressed, followed by hot air drying.

This method requires a large amount of steam and many steps.
The disadvantage is that the device is large-scale.

On the other hand, the method using a vent extruder eliminates the above-mentioned drawbacks and is economical, but it is difficult to remove the solvent sufficiently.

In order to improve the solvent removal effect of the extruder, improvements to the structure of the extruder and methods of injecting and mixing foaming agents such as water into the extruder have been carried out (Japanese Patent Publication No. 54-12949, Japanese Unexamined Patent Application Publication No. 1983-1989).
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However, with the method of injecting and mixing water into an extruder, it is difficult to uniformly disperse water in a rubber solution. Therefore, it is necessary to provide a mixing section in the extruder or to lengthen the cylinder of the extruder.

In order to improve mixing, it has been proposed to concentrate the elastomer solution and add and mix water and a surfactant (Japanese Patent Laid-Open No. 59-91101).

However, this method requires a step of concentrating the elastomer solution, which is undesirable because surfactant is mixed into the rubber after solvent removal.

The purpose of the present invention is to solve the above-mentioned drawbacks, to efficiently remove the solvent and unreacted 1,3-butadiene from a polybutadiene solution using a C4 fraction containing cis-2-butene as the main component, and to remove the remaining volatiles. The objective is to obtain polybutadiene with less oxidation.

[Means to solve the problem]

The present invention is based on a polybutadiene solution obtained by polymerizing 1,3-butadiene monomer in a polymerization solvent containing cis-2-butene as a main component, based on 100 parts by weight of polybutadiene in the solution,
The above problems were solved by providing a method for drying polybutadiene, which comprises adding and mixing 0.1 to 30 parts by weight of water and then removing the solvent using an extruder.

In the present invention, C containing cis-2-butene as a main component
The 4 fractions are, for example, cis-2-butene and trans-2-
It is a C4 fraction containing 50-t% or more of butene, and may contain hydrocarbon solvents such as trans-2-butene, n-butane, butene-1, propane, and ethane in addition to cis-2-butene. .

Particularly preferred solvents are cis-2-butene and trans-2-butene.
Solvents consisting essentially of butene are preferred.

50wt% cis-2-butene and trans-2-butene
Below, the solubility of polybutadiene decreases.

In addition, cis-2-butene, which is an impurity (approximately Q, 5evt% included) in the 1,3-butadiene monomer accumulated in the plant during the long-term polymerization of 1,3-polybutadiene, is also used as a solvent. It can be preferably used.

The present invention is applied to polybutadiene solutions using these C4 fractions as solvents, and is suitable for polybutadiene solutions containing unreacted 1,3-butadiene polymerized in a polymerization solvent mainly composed of cis-2-butene. .

The polybutadiene in the present invention is, for example, high cis-1,
Examples include 4-polybutadiene, low cis-1,4-polybutadiene, and high vinyl polybutadiene.

Polybutadiene concentration in polybutadiene solution is 5-40
-t%, preferably 10 to 3011%.

If it is more than 35 wt %, the solution viscosity is too high and it is difficult to mix and disperse water, and if it is less than 5 @ t %, it is not economical.

The amount of water added is 100% of the polybutadiene in the mixed solution.
The amount is 0.1 to 30 parts by weight, preferably 1 to 10 parts by weight. If it is less than 0.1 parts by weight, the desolvation effect will not be sufficient, and if it is more than 30 parts by weight, a large amount of energy will be required to evaporate the water and the extruder temperature will need to be raised to a higher temperature.

In the present invention, water is added in advance to a polybutadiene solution with a low melt viscosity after polymerization and mixed, so that water is uniformly and finely dispersed in the solution. It is thought that this increases the efficiency of removing the solvent and unreacted 1,3-butadiene by the extruder thereafter.

The exit temperature of the extruder is 130 to 170°C, and the process can be carried out at a relatively low temperature, and there is no burning, gelling, or coloring, and there is no effect on physical properties.

The extruder used is not particularly limited, but a vent extruder with a single shaft or multiple shafts and provided with several vent holes is used. - [Effects of the Invention] The present invention is characterized by mixing and dispersing water into a polybutadiene solution obtained by polymerizing 1,3-butadiene in a solvent containing cis-2-butene as a main component, and then applying this to an extrusion dryer. Polybutadiene with a residual amount of solvent of 0.1% by weight or less can be obtained.

〔Example〕

Example 1 1.3-butadiene 30wt%, cis-2-butene 56
Yoke t%, trans-2-butene 13wt%, balance n-
After polymerizing 1,3-butadiene in a monomer solution of butane, propane, ethane, etc. using a cobalt octoate, O-diethylaluminum monochloride catalyst, and using 1,2-butadiene as a molecular weight regulator, 2,
Polymerization was stopped by mixing 0.5 phr of 6-di-tert-butylphenol to the polymer with a small amount of water;
A 16-t% solution of cis-1,4-polybutadiene was obtained. This cis-1,4-polybutadiene has a Mooney viscosity of M
L. , (100°C) is 42, cis content 98.3
%Met.

50 per hour of this polybutadiene solution! (approximately 30 uglies, approximately 4.8 kg of polybutadiene) per hour
f at 40°C and subsequently mixed in a mixer.

Next, this mixed solution was fed to a vent extruder to remove the solvent. The vent extruder used was a twin-screw one with a screw diameter of 125 days, an L/D ratio of 10, and two vent holes.

The operating conditions for the extruder were a screw rotation speed of 50 revolutions per minute, a temperature of 150°C from the jacket, suction at the vent with a vacuum pump, and a temperature of 76°C at the first vent (behind the hopper).
0 Torr, 2nd hent (extrusion direction side) 100 Torr
It was set as r.

The obtained cis-1,4-polybutadiene conforms to JISK63
The residual volatile content (solvent + water) was determined to be 0.2% by the 83 mil oven method. In addition, residual volatile content is 0.2%
The breakdown was 0.05% solvent and 0.15% water.

Comparative Example 1 The operation was the same as in Example 1 except that water was added at the second vent inlet of the vent extruder at a rate of 0.25 f/hr. The obtained cis-1,4
- The residual volatile content of polybutadiene was 2%. The breakdown was 10.41% remaining solvent and 1.59% water.

Claims (1)

[Claims] For a polybutadiene solution obtained by polymerizing 1,3-butadiene monomer in a polymerization solvent containing cis-2-butene as a main component, 0.0.
A method for drying polybutadiene, which comprises adding and mixing 1 to 30 parts by weight and then removing the solvent using an extruder.