JPH0359084B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the prevention of retention burn in a preliminary zone of a rubber-containing styrenic resin prepolymer having a monomer in a continuous bulk polymerization method of rubber-containing styrenic resin. .

<Prior Art> As a continuous bulk polymerization method for rubber-containing styrenic resin, there has conventionally been a method in which preliminary polymerization is performed in a polymerization tank and then devolatilization is performed in a demonomer machine. In this case, a heating device is installed between the polymerization can and the demonomer machine to preheat the prepolymer, and then the prepolymer is supplied to the demonomer machine.

As conventional preheating methods, shell-and-tube heat exchangers, single-tube jacket heating, and line mixers with jackets are often used.

In this method, if the viscosity of the prepolymer is high, there will be little renewal of the prepolymer on the wall surface, and it will remain as a stagnation material, so if heating continues for a long time, it will turn into a burnt black polymer and mix into the product, so the operation must be stopped. I have no choice.

Methods to prevent this are to dilute the prepolymer with a solvent to lower its viscosity, and to lower the solid content concentration (polymerization rate) of the prepolymer, but this method reduces the heat load in the demonomer machine. Due to this increase in size, the heating temperature in the preheating zone must be increased, which likewise results in retained burnt polymer on the wall surface.

Furthermore, when liquid additives are mixed into the prepolymer, there is a problem that the additives are blown out by the demonomer, and the additives are not mixed uniformly or cannot be added in large quantities.

<Problems to be Solved by the Invention> The present inventors have overcome these drawbacks, and have achieved a system that prevents prepolymer retention in the preheating zone even during long-term continuous operation, prevents burnt polymer, and efficiently processes prepolymer. I found a way to preheat it.

<Means for Solving the Problems> The present invention provides a method for supplying a rubber-containing styrenic resin prepolymer having a monomer to a screw extruder having a heat generating function through shear mixing, heating it, and adjusting the pressure to maintain the prepolymer in a liquid state. This is a method for producing a rubber-containing styrenic resin, which is characterized in that it is then fed to a heated demonomer machine to evaporate and remove the monomer.

In the present invention, the prepolymer supplied to the screw extruder preferably has a fixed content concentration of 30 to 80% because the viscosity is appropriate.

In the present invention, the screw extruder having a heat generating function by shear mixing means that heat is generated by friction of the prepolymer.

The screw extruder used in the present invention preferably has a cylinder length/cylinder diameter of 5 to 30, and the screw shape and number of screw shafts are not particularly determined.

It is desirable to select a screw rotation speed within the range of 100 to 300 rpm at which the prepolymer is heated to 150 to 190° C. by heat generated by shear mixing.

In the present invention, it is important that the prepolymer heated in the screw extruder is in a liquid state. If it is not liquid, it will not be possible to heat it uniformly, and the solid content and gas phase will separate, resulting in the generation of heat-degraded products that remain in the line.

For this reason, for example, the pressure is controlled by a control valve, orifice, etc. attached to the outlet of the extruder so that the monomer does not evaporate when the prepolymer is heated.

In the present invention, the liquid prepolymer is then fed to a demonomer. The demonomer machine needs to be heated, but the heating temperature is 190-230℃
is desirable. This is because the monomer can be effectively removed by evaporation without thermally deteriorating the prepolymer.

In the present invention, the monomer removal machine includes, for example, 1
An extruder with a shaft or twin-screw ventro is used. In this case, the evaporated monomer is removed through the vent.

In the present invention, when mixing additives with the prepolymer, before feeding it to the screw extruder,
Preferably, they are mixed in advance.

<Example> Example 1 Rubber content: 20% by weight Styrene content: 56 〃 Acrylontrile 24 〃 Raw materials with the following composition were polymerized in a polymerization tube at 110°C using a continuous polymerization apparatus as shown in the figure to form a solid. Min concentration 70%
After that, it is fed to the screw extruder 2 heated to 170℃ with screw diameter: 90 mm, cylinder length / cylinder diameter = 15, and the screw rotation speed is increased.
While kneading at 200 rpm, the pressure at the exit of the screw extruder was controlled to 15 Kg/cm ² G using control valve 3, and the polymer temperature at the exit of the extruder was 170°C. As a result of continuous bulk polymerization using the method of supplying monomer to demonomer machine 4, the amount of residual monomer in the polymer was 0.1% or less, and no foreign matter was found in the polymer due to retention burns even after 4 months of continuous operation.

Example 2 Solid content concentration was determined using the same equipment and raw materials as Example 1.
After setting it to 50%, the screw rotation was set to 300 r.pm, the extruder outlet pressure was set to 20 Kg/cm ² G, and the extruder exit polymer temperature was adjusted to 50%.
As a result of operating in the same manner as in Example 1 at 180°C,
The amount of residual monomer in the polymer was 0.15%.

Example 3 Using the same equipment as in Example 1, 1.5 parts by weight/(100 parts by weight of polymer) of a liquid additive was added before the screw extruder, and the mixture was uniformly kneaded by the screw extruder and passed through the demonomer nozzle and Additives no longer spray out from the vent port.

Comparative Example 1 In the apparatus shown in the figure, the same raw materials as in Example 1 were subjected to continuous bulk polymerization in the same manner using a double tube with a jacket, inner diameter 90 mmφ, 5 m, and a jacket temperature of 200°C instead of the screw extruder. result,
The amount of monomer remaining in the polymer was 0.5%, and after one month, foreign matter due to retention burn began to enter the polymer, so the entire system was shut down and the double pipe was examined.
Burnt blackish-brown polymer was attached to the wall.

Comparative Example 2 As a result of continuous bulk polymerization using the same equipment as in Comparative Example 1 and using the same raw materials and solid content concentration as in Example 2, the amount of residual monomer in the polymer was 1.0%, which was 1.5%.
After several months, foreign matter due to retention burn started to get mixed into the polymer.

<Effects of the Invention> The present invention provides the following advantages: (1) By supplying a rubber-containing styrenic resin prepolymer containing a monomer to a heated demonomer machine in liquid form, (1) the prepolymer is constantly renewed on the wall surface, so that the prepolymer is constantly renewed; Since it is not heated for a long time, burnt polymer does not occur.

(2) Since the shear heat generated by the screw can be transferred to the prepolymer, it can be efficiently prepared.

(3) By preheating the prepolymer to a high temperature, the load on the monomer removal machine in the next step can be reduced, so it is possible to efficiently remove residual monomer. At the same time, product quality improves.

(4) Since it is kneaded using a screw, it is easy to mix additives into the prepolymer.
And it can be heated evenly.

[Brief explanation of drawings]

The figure is a flow diagram illustrating one embodiment of the invention. 1...Polymerization can, 2...Screw extruder, 3...
...control valve, 4...monomer removal machine.

Claims (1)

[Claims] 1. A rubber-containing styrenic resin prepolymer having a monomer is supplied to a screw extruder having a heat generation function by shear mixing, heated, and adjusted to a pressure that keeps the prepolymer in a liquid state, and then supplied to a heated demonomer machine, A method for producing a rubber-containing styrenic resin, characterized by removing monomer by evaporation.