JPS583481B2 - Bulk polymerization reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bulk polymerization reactor, and more specifically, the bulk polymerization reactor has a stirrer in the can, and the shaft of the stirrer is eccentric. The distance between the center of the can and the center of the eccentric shaft is 15 of the shaft equivalent diameter.
0% or less, and the agitator has blades for scraping the walls of the premises, and the agitator is equipped with a perforated plate with an open area ratio of 35 to 65%. The present invention relates to a characteristic bulk polymerization reaction apparatus.

Emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization are known as methods for industrially producing plastics using polymer production reactions.

These polymerization methods are sometimes selected depending on how the resulting plastic will be used, but in general, they are limited by the removal of polymerization reaction heat and the handling of viscous substances that increase as the polymerization reaction progresses. It is currently selected.

When viewed as a polymerization reaction process, the bulk polymerization process is preferable as an industrial-scale polymerization process because it is easy to adopt the Claude system and is a resource-saving, energy-saving, and low-pollution process. It is necessary to solve difficult problems with reaction equipment, such as appropriate equipment that can handle substances whose concentration increases exponentially without abnormal retention, and heat removal area that decreases as the scale increases. Comparatively, success has been achieved with only a very small number of types of plastics.

Generally, in bulk polymerization reactions, the viscosity of the system increases as the polymerization reaction progresses.

It is extremely difficult to stably handle such highly viscous substances within a reactor.

That is, an immovable layer, so-called abnormal stagnation layer, grows on the wall surface of the premises and near the stirring axis.

Since this layer remains at high temperatures for a long time, polymers with poor thermal stability may deteriorate, become colored, and eventually carbonize.

The polymer in these abnormal retention areas is dislodged by the flow of the polymer, causing the normal polymer to become colored, or being mixed into the normal polymer as carbonized foreign matter (carbide), thereby significantly impairing its quality.

Conventional solutions to eliminate these abnormal retention areas have been to use screw-type equipment that applies shear to increase the shear rate on the wall surface as much as possible, or to use equipment that has a special kneading function. Not only does it consume a significant amount of power for mixing, but it also raises the temperature within the liquid phase due to frictional heat, further accelerating the deterioration of polymers with poor thermal stability, and making it difficult to control the polymerization reaction. It was normal to be.

Another method is to complete the reaction in a state where the liquid phase has low viscosity without increasing the polymerization rate and recover the polymer. Although stable handling can be avoided, there are disadvantages in that the efficiency of the device deteriorates and the monomer recovery process becomes complicated.

Another problem associated with bulk polymerization reactors is reaction instability.

Generally, a polymerization reaction is an exothermic reaction, and controlling the reaction heat is difficult due to the high viscosity of the system, which may lead to the generation of hot spots and runaway polymerization.

In view of this situation, the present inventors have made extensive research efforts to develop an apparatus suitable for bulk polymerization reactions, and have arrived at the present invention.

The monomer species that can be used for bulk polymerization in the polymerization reaction apparatus of the present invention may be any monomer that can perform bulk polymerization such as styrene, styrene-acrylonitrile copolymer monomer, rubber-containing acrylonitrile-styrene copolymer monomer, nylon, polyester, etc. It can also be applied to those that cause condensation polymerization and addition polymerization reactions.

It is particularly advantageous for thermal bulk polymerization of thermochromic, transparent polymer species or for bulk polymerization reactions using radical polymerization catalysts.

The term "bulk polymerization" as used herein includes solution polymerization of 30% by weight or less.

FIG. 1 shows an example of a bulk polymerization apparatus according to the present invention.

The content and effects of the present invention will be explained in more detail with reference to this figure.

A is a polymerization tank, which has a jacket tank structure and is capable of heating, keeping warm, or cooling as appropriate.

B is a stirring shaft having a structure in which the shaft center is eccentric from the center of the polymerization tank body in the gas phase portion.

The stirring shaft must be eccentric from the gas phase to the liquid phase, and the amount of eccentricity is such that the distance between the center of the can and the center of the eccentric shaft (distance between the shafts) is 150% or less of the shaft equivalent diameter.

More preferably, it is in the range of 10 to 110%.

According to a detailed study of the ABS bulk polymerization reaction by the present inventors, when the distance between the shafts is O (in the case of concentric shafts), the stagnant layer grows significantly around the shaft when the elapsed continuous operation time of the polymerization reaction exceeds 3 days. It has become clear that the colored phase or gel phase is mixed into the product, resulting in a colored resin or the formation of protrusions on the surface of the product, which significantly impairs the product value.

If the agitation shaft of the liquid phase section is made eccentric, the stagnant layer around the shaft is almost eliminated.

However, if the amount of eccentricity exceeds 150% of the diameter of the eccentric shaft, the behavior within the polymerization reaction plant will not become stable, although this is effective in preventing the growth of an abnormal accumulation layer in the stirrer.

That is, in order to prevent abnormal retention in the stirrer and to stabilize the polymerization reaction, the distance between the center of the polymerization tank and the center of the stirring shaft must be 150% or less of the equivalent diameter of the stirring shaft.

More preferably, it is in the range of 10 to 110%.

C is a scraped wing.

This scraping blade rotates together with the stirrer, and is essential for eliminating abnormal accumulation on the inner wall surface of the polymerization tank.

The clearance between the scraping blade and the inner wall surface of the tank should be as small as possible in view of the required functions, but it is usually within 60 mm, preferably within the range of 5 to 25 mm.

There is no particular restriction on the number of stirrings, and as long as the stirring speed is 1 rpm or more, it is effective to prevent a polymer retention layer from forming on the walls of the polymerization tank.

However, if the speed is 30 rpm or higher, vertical mixing in the polymerization tank becomes intense, which not only makes the reaction in the tank unstable, but also increases the consumption of stirring power, which is generally undesirable.

The scraping blade must be installed so that its scraping area usually scrapes 80% or more, preferably 101% or more of the liquid phase wall area.

If the scraped area is too small, a stagnant layer will form on the unscraped walls of the premises, causing discoloration and dirt contamination.

D is a perforated plate.

This perforated plate rotates together with the stirrer, and its aperture ratio is preferably in the range of 35 to 36% of the internal cross-sectional area.

This porous plate is for maintaining the stability of the reaction of the reaction solution in the tank.

That is, the purpose is to stabilize the reaction by suppressing vertical mixing in the tank and stabilizing the fluid state.

If a perforated plate with an aperture ratio of less than 35% is used, a high polymerization rate of 98% can be ensured at the exit from the polymerization tank, but as the operation progresses, the product becomes colored and the amount discharged decreases. Observation of the perforated plate of the agitator after the machine was shut down revealed that colored polymer was deposited on the perforated plate surface, which is not desirable.

Furthermore, when bulk polymerization was carried out using a porous plate with an aperture ratio exceeding 65%, the internal pressure was not stable, the temperature distribution was extremely unstable, and the discharge of the polymer tended to be unstable.

The single hole shape of the perforated plate D is generally circular, but it is not necessarily circular and may be of any shape as required, such as a slit shape, a polygonal shape, or an arc shape.

On the other hand, the size of the single pore is important as well as the pore opening ratio, and it goes without saying that it is necessary to select an appropriate size according to the viscosity of the polymer to be handled.

The effects of the present invention have been explained above based on FIG. The scope of the invention is extremely wide, and the invention is not limited to the limited illustrations in the specification, but any device that satisfies the contents described in the claims is included in the present invention.

Examples will be described below.

Example 1 Polybutadiene (FRS-20 manufactured by Firestone)
04) Styrene/acrylonitrile was polymerized according to the following polymerization recipe in the presence of latex to obtain a polymer latex in which styrene/acrylonitrile was graft copolymerized onto polybutadiene.

The polymerization rate was 9.5%.

Graft copolymerization formulation material Materials Charged parts Polyfukudiene latex (solid content) 700 Styrene 21.6 Acrylonitrile 8.4 Tertiary decyl butane 0.1 5 Sodium laurate 1.50 Textulose 05 Clondroperoxide
02 Sodium pyrophosphate
03 Ferrous sulfate 001
Ion-exchanged water 1 5 0.0 25 parts by weight of styrene monomer were added to 25 parts by weight of this latex solid content, and after stirring well, 08 parts of magnesium sulfate was added.

The mixed solution was separated into a white polymer/monomer phase (crumb) and water, dehydrated, and only the polymer/monomer phase (crumb) was taken out, containing 29 parts of styrene monomer and 2 parts of acrylonitrile monomer.
1 part and 0.15 part of normalized decyl mercabutane were added to prepare a homogeneous solution (raw material dope).

The raw material dope composition is as follows.

ABS 25 parts by weight Styrene monomer 54 〃 Acrylonitrile monomer 21 〃 Water 1O 〃 This raw material dope was preliminarily bulk polymerized to a solid content of 50% by weight, and was continuously polymerized to 95% in the polymerization tank shown in Figure 1.
The ABS resin was thermally polymerized until the end of the resin was heated, the unpolymerized monomer was separated, and the ABS resin was continuously taken out.

The dimensions of the polymerization tank in FIG. 1 are as follows.

Polymerization tank inner diameter 750mmφ Stirrer shaft diameter 150mmφ Distance between eccentric shafts 50mm Height to liquid level 2355mm Capacity approx. 900l Perforated plate opening ratio 51% (single hole diameter 50mmφ) Polymerization conditions Raw material dope processing speed 150kg/H Internal pressure
2.0kg/cmG Polymerization temperature T1 120±2°CT2 13
Continuous operation was performed for 240 hours under the following conditions: 0±2°C T3 160±2°C T, 180±2°C 'r, 200±2°C.

The polymerization conditions were stable, and the resulting resin was an ABS pellet with stable physical properties and color tone.

Melt viscosity 4. O x 10” poise (2208C0.5mmφx 1. O mm L,
5 0kg/cm) Tensile strength 4 1
0 kg/cm breaking elongation 18% Izod impact strength 22 kg/cm/cm notched Yel lowness Index 2 6~28
% Comparative Example 1 The same raw material dope as in Example was continuously polymerized in the following Teimension polymerization tank.

Polymerization tank inner diameter 750mmφ Stirrer shaft diameter 150mmφ Distance between eccentric shafts Omm Height to Nada surface 2355mm Capacity Approximately 900l Perforated plate opening ratio 51% Perforated plate single hole diameter 50mmφ Polymerization conditions Raw material dope processing speed 150kg/H Internal pressure 2.0kg/ cmG polymerization temperature T1 125±2°C T2 137±2°C T, 165±2°C T4 188±5°C T, 205±7°C Continuous operation was performed under the above conditions, but after 70 hours the pellet color changed. He became restless, and after 150 hours, red-black foreign matter began to be mixed in the resin.

The physical properties of the obtained resin are as follows. Melt viscosity 4
．． O x 103 poise (220°G O. 5 mm x 1
．． Ommφ, 50 kg/cm) Tensile strength
4 1 0kg/cm breaking elongation 16
% Izod impact strength 20kg・cm/cm Notched Y
el Iownes. s Index 2 8 ″6
After the 0% operation, the polymerization tank was dismantled and the agitator was observed, and a red colored resin phase was found to form a layer of about 10 mm on the lower shaft of the polymerization tank.

Comparative Example 2 Continuous polymerization was carried out under the same conditions as in Example 1, but with a perforated plate having an aperture ratio of 20%.

Raw material dope processing speed 150kg/H internal pressure
2.0kg/cmG polymerization temperature
T1 125±2°C T2 140±2°C T3 170±2°C T4 195±2°C T, 209±2°C The physical properties of the obtained resin are as follows.

Izod impact strength 18-20 kg/cm/cm Notched Yet Iownese Index 3 5'4
5% Comparative Example 3 Continuous polymerization was carried out under the same conditions as in Example 1, but with a perforated plate having an aperture ratio of 70%.

Raw material dope processing speed 150 kg/H Internal pressure
2.0kg/cmG polymerization temperature
T, 125±5°CT2 135±5°C T3 165±5°C T, 183±10°C T, 205±10°C The temperature distribution inside the polymerization tank was disturbed, and the physical properties and color tone of the resin were also unstable. .

Izod impact strength 18-24kg・cm/cm Notsuchi Yellowness Index 23-3
2%

[Brief explanation of drawings]

FIG. 1 shows an example of a cross-sectional view of a bulk polymerization apparatus according to the invention. FIG. 2 shows a sectional view taken along the line XX in FIG. 1. A: Polymerization tank body, B: Stirring shaft, C: Scraping blade, D: Perforated plate, I: Supply port, H: Discharge port, X: Distance between eccentric shafts, d
: Stirring shaft diameter.

Claims (1)

[Claims] 1. An eccentric stirrer shaft is installed in the can of the bulk polymerization reaction tank, with the distance between the center of the can and the center of the shaft of the stirrer being eccentric within a range of 150% or less of the shaft diameter of the stirrer, and an eccentric stirrer shaft attached to the inner wall of the tank is installed. Wings for scraping the polymer and an opening area ratio of 3
A bulk polymerization reaction apparatus equipped with a stirrer equipped with a 5-65% perforated plate.