JPS5849710A - Defoaming method in preparation of vinyl chloride polymer and polymerizing apparatus - Google Patents

Abstract

PURPOSE:The titled apparatus, having rotating blades with the top cover in the vapor pahse part of a vessel for polymerizing vinyl chloride in an aqueous medium, capable of breaking and defoaming air bubbles in large quantities with certainty, and effective for improving the productivity, yield and quality and preventing the scale deposits. CONSTITUTION:A reflux condenser 6 is provided on a stainless steel polymerizing vessel 1, and two paddle blades 4 for defoaming are provided in the upper stage of an agitating shaft 2 not in contact with a polymerization phase in addition to agitating blades 3, e.g. paddle type, for agitating the polymerization phase, and covers 5 and 5' are mounted on the blades 4. Vinyl chloride or a monomeric mixture consisting of the vinyl chloride essentially, e.g. a mixture of ethylene with vinyl acetate, is polymerized in the presence of a polymerization initiator, e.g. di-2-ethylhexyl peroxydicarbonate or K2S2O8, and a dispersion assistant, e.g. partially saponified polyvinyl alcohol, in an aqueous medium in the vessel 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defoaming method and a polymerization apparatus for producing a vinyl chloride-based monomer.

Conventionally, methods of adding an antifoaming agent or breaking foam using mechanical means have been proposed as methods for defoaming foam generated from the liquid surface during polymerization of vinyl chloride or the like. However, the method of adding an antifoaming agent has a considerable effect on foaming caused by an aqueous suspending agent solution that is not yet accompanied by many polymer particles, which occurs relatively early in the suspension polymerization of vinyl chloride. Although the effect is recognized,
However, since the foam is accompanied by a large amount of polymer particles (polyvinyl chloride particles), the desired defoaming effect cannot be obtained.

A specific method for defoaming dough using mechanical means is "Fluid spray method &("Polymer manufacturing process" by Koji Saeki, Kogyo Choushikai Publishing, published March 20, 1977, M84 edition, $283 page). Or “rotary defoaming 1!1
''' [Defoaming device manufactured by Ahemap in Switzerland, Pro
oesaBioohem, June.

37 (1972)), but in both cases the equipment is complicated, and not only do they have problems in terms of maintenance management and economic efficiency, but also the polymerization vessel has to be large, and it is not sufficient to handle a large amount of foam. It has the disadvantage of being unable to produce effective results.

Therefore, in order to avoid the negative effects of foam generation as much as possible, methods such as reducing the charge amount at the start of polymerization to increase the gas phase inside the polymerization vessel, and removing heat from the reflux condenser and removing unreacted monomers, A method of controlling the recovery speed has generally been adopted.

As a result of observation and research on the generation of bubbles and the breaking of bubbles by mechanical means, the present inventors found that bubbles are generated on the liquid surface during illegal condenser operation and when recovering unreacted monomer after the completion of the polymerization reaction. It was confirmed that a large amount of polymer particles were deposited on the liquid surface, and the foam was apparently dehydrated by the drainage action of gravity, forming a solid foam with poor fluidity. Although foaming is quite effectively eliminated by mechanical foam breaking (impact and shear), it is still not sufficient, and at the same time, foam containing polymer particles is scattered from the tips and upper ends of the rotating blades, and these bubbles enter the polymerization vessel. It was found that in addition to adhering to the inner wall of the lid and forming scale, it also caused blockage of the raw material inlet, reflux condenser series connection, unreacted monomer recovery vibro, etc.

The present invention has solved these problems, and is aimed at the gas phase in the polymerization vessel when vinyl chloride monomer or a monomer mixture mainly composed of vinyl chloride is polymerized in an aqueous medium. By providing a rotary vane on the rotary vane and installing a cover on the rotary vane, bubbles generated on the liquid surface during polymerization and during recovery of unreacted monomer after completion of polymerization are broken by the rotary vane. The present invention also relates to a defoaming method in the production of a vinyl chloride polymer, characterized in that scattering due to foam breakage is prevented by the cover. This is what we provide. 'According to the present invention, a large amount of bubbles generated on the liquid surface is reliably broken and extinguished, and bubbles are prevented from scattering to the upper part of the polymerization vessel. As a result, the amount of heat removed by the reflux condenser is increased, and the amount of heat removed by the reflux condenser is increased. Improved productivity, yield, and quality by shortening reaction monomer recovery time (fisheye, etc.)
This has the effect of improving industrial properties and preventing scale adhesion on the walls of the gas phase in the polymerization reactor, which is extremely noteworthy from an industrial perspective.

The explanation will be based on the aspect of the polymerization apparatus Io related to the present invention.

- Figure 141 is a schematic diagram showing the configuration of the polymerization apparatus of the present invention. In the figure, 1 is a combiner main body, 2 is a rotating shaft, and this rotating shaft has stirring blades 8 for stirring the polymer solution, A rotating vane 4 and a cover 5 are provided for defoaming. The cover 5 is fixed to the rotating shaft 2 or the rotating blade 4 (
(See Figure 182).

The foam F generated from the liquid level is broken and broken mechanically (shear force, impact force) by the rotating blade 4 rotated by the rotating shaft 2.
At that time, the foam scattered from the tip of the rotary blade 4 is stopped by the cover 5 and is defoamed. In addition,
6 is a reflux condenser provided as necessary, 7 is a drive motor, and 8 is a pipe for charging raw materials and recovering unreacted monomers.

Regarding the rotating blades 4, there are no restrictions on the shape or number of blades, such as paddle type, turbine type, Faudler type, propeller type, etc., and the point is to apply shear force and impact force to the bubbles to effectively break and defoam them. It is acceptable as long as it can be achieved.

It is convenient in design to install the rotating blade 4 so that it rotates coaxially with the rotating shaft for stirring the polymerized phase, but it does not necessarily have to be coaxially, and the rotating shaft is free. It may also be installed in the same state and rotated by another power source.

The size of this rotating blade is 0.2 of the inner diameter of the polymerization vessel.
It is preferable to set the ratio to at least 0.3 times or more, and if it is smaller than this, it becomes difficult to break the bubbles rising from the polymer phase liquid level near the i-combiner wall.

For the purposes of the present invention, it is desirable that the polymerization phase liquid level δ be close to 20,000.

However, if this rotary vane is too close to the liquid surface of the first combined phase and comes into contact with the agitated and fluidized polymer phase, it will have an adverse effect on the formation of polymer particles through polymerization, so such contact must be avoided. . The adverse effects of this contact are particularly large during the initial stage of the polymerization reaction (until the polymerization rate reaches approximately 5%). Therefore, after the start of polymerization and until the polymerization rate reaches about 5%, the rotating blades should be positioned so that there is a distance between them and the liquid level of the polymerization phase.

Next, the cover 6 installed on the rotary vane 4 prevents bubbles that are self-dispersed from the tips and upper ends of the vane due to the centrifugal force caused by the rotation of the rotary vane 4, and the collision action at that time causes the bubbles to break and break.
In addition to defoaming, it also reduces or eliminates the kinetic energy of the flying bubbles, completely preventing them from flying upwards.
Combined phase liquid level heat = indicates the function of effectively defoaming foam and controlling the foam level to a constant level.

The shape and installation method of this cover 5 are determined individually depending on the shape of the rotating blade 4, etc.
Figures 3 and 3 illustrate this. In other words, Figure + IL) shows a situation where two paddle blades are conveniently used as the rotary blade 4 (tl::, above the left and right paddle blades C; a fan-shaped cover 5' is installed). Then, this cover 5' rotates together with the rotary blade 4 for defoaming. Figure (b) shows a vertical cross-sectional view of the ((trans)) factor. Figures 3 and 5 are separate. This shows the aspect of.

The cover 5' is fixed to the rotating shaft so as to cover the entire rolling surface 1 of the rotating blade 4. Moreover, the cover 5# is a cover C: attached diagonally to the top of the paddle blade.

The number of blades of the rotating blade 4 may be 3 or 4.

$4S is a vertical sectional view showing the positional relationship between the rotating blade 4' and the cover 5 that covers it. General C Since the amount of scattering from the vicinity of the tip of the two blades is large, it is necessary to cover the entire area near the tip with a cover, and the O/l) as shown in the figure should be 1.0 or less, preferably 0.8 or less. It is best to determine the cover at the upper end of one blade so that a/b is O, S a lower C:. It is determined as appropriate, taking into account the shape, change in bubble scattering angle, etc. Further, in order to facilitate operations such as washing with water and applying a scale preventive agent, there is no problem in taking measures such as making a minimum number of holes in the cover or devising the shape of the cover.

The method of the present invention can be applied to, for example, suspension polymerization, emulsion 1 method, etc. when vinyl chloride monomers are polymerized in an aqueous medium, and is particularly effective in suspension polymerization.

Polymerization is not limited to vinyl chloride alone, but may also be copolymerization of vinyl chloride and other monomers, such as ethylene, propylene, vinyl acetate,
Examples include vinyl propionate, lauryl vinyl ether, isobutyl vinyl ether, ethyl acrylate, and butyl acrylate.

The polymerization initiator may be an oil-soluble catalyst or a water-soluble catalyst conventionally used in the polymerization of vinyl chloride monomers. Examples of the oil-soluble catalyst include azobis-a, α'-dimethylvaleronitrile, and 2,2'-azobis- Azo compounds such as 2,4-dimethyl-4-methoxyvaleronitrile, cyisopropyl peroxyv dicarbonate, di-2-ethylhexyl peroxydicarbonate, di(β-ethoxyethyl) peroxyv dicarbo $-), 1 Examples include peroxides such as -butylperoxyneodecanate, acetylcyclohexylsulfonyl peroxide, t-butylperoxyv biparate, and lauroyl peroxide. In addition, water-soluble catalysts include potassium persulfate, ammonium persulfate,
Examples include hydrogen peroxide, cumene hydroveroxide, and the like. The dispersion aid for the monomer in the aqueous medium may be any conventionally known agent, including styrene-maleic acid copolymer, partially saponified polyvinyl alcohol, methyl cellulose, hydroxypropyl methyl cellulose,
Ethyl cellulose, gelatin, charcoal 111 calcium,
Calcium phosphate, sodium lauryl sulfate, sorbitan monostearate, dodecylbenzene sulfonic acid F
Examples include Rikumu and the like.

Other conventional additives, such as polymerization degree regulators, crosslinking agents, stabilizers, fillers, antioxidants, degreasers, scale inhibitors, etc., may also be added.

As described above, the present invention establishes a method for defoaming foam generated during the production of vinyl chloride polymers, and has great industrial value.

The present invention will be described below with reference to specific examples, but the present invention is not limited thereto.

Example 1 A reflux condenser with a heat transfer area of 7.5 mm was attached to a stainless steel polymerization vessel with an internal volume of 2.1 m (inner diameter of 1.05 m),
Inside the polymerization vessel, in addition to the usual paddle-type stirring blades for stirring the polymerization phase, there is also a paddle-type 2 with a diameter (d) of 400cm and a width (b) of 50cm on the upper stage of the stirring shaft that does not come into contact with the liquid phase during polymerization. A blade (rotating blade for defoaming) was attached, and a cover shown in FIG. 2(a) was attached to the blade with a clearance of 18 mm from the upper end of the blade. However, in that case W&3
The dimensions corresponding to figures a and 0 were as shown in Table 1.

This polymerization vessel was charged with 90011 p of deionized water, 600 g of partially saponified polyvinyl alcohol, and 300 g of di-2-ethylhexyl peroxydicarbonate, and the inside of the polymerization vessel was degassed to 50-Hg. Pour 6009 vinyl monomers and set the rotation speed of the stirring shaft to 230 rp.
While stirring at m, the temperature was raised to 57°C to conduct polymerization.

In addition, from 1 hour after the start of polymerization, 30
000 Kcal/)I was removed until the end of 1 cup.

The polymerization reaction was stopped when the internal pressure of the first reactor dropped to 6.5 Kll/cd Ck, and unreacted monomers were recovered at a low rate that did not cause foaming in the reactor. Next, after removing the slurry-like polymer content, the stirring is stopped and the degree of polymer adhesion on the wall inside the polymerization vessel is examined, as well as the adhesion status of polymer particles inside the reflux pumpdenser. confirmed.

The adhesion height (wn) of polymer particles to the inner wall of the polymerization vessel is:
It was measured as a wall reference on the extension of the lower end surface of the rotating blade for defoaming.

Further, in this apparatus, the distance between the lower end of the rotating blade and the nozzle connecting the reflux condenser at the top of the first mixer and the nozzle for collecting unreacted monomers was 600 mm.

The results are shown in Table 181.

However, the "product fisheye (number of pieces)" in the same table is
Polymer powder (product) 50? ,DOP25? , tribasic lead sulfate 0.3, lead stearate 1.0? , titanium oxide 0
．． 01j', carbon black o, and oosIP were mixed, left for 30 minutes, kneaded for 7 minutes with a roll at 140°C, and taken out from the roll as a 0.2-thick sheet. The number of transparent particles (fish eyes) is counted.

As can be seen from Table 1 of Table 111, in actual M and %3, there was little cover in the upper direction of the rotating blade, and therefore, it was not possible to sufficiently prevent scattering, and in experimental rot 5, there was less cover in the lateral direction of the rotating blade. Because there was no cover, it was not possible to prevent scattering.

Example 2 In Example 1, in the gas phase section at the upper stage of the stirring shaft, a diameter of 40
0■, with a paddle-shaped two-blade installation with a width of 50 cm, the polymerization reaction was carried out without using a reflux condenser, and as the polymerization approached the end, the pressure inside the polymerization vessel decreased to 6.51P/-G. At this point, the polymerization reaction was stopped, and while stirring was continued, the unreacted polymer was recovered from the recovery pipe at the top of the polymerization vessel at a rate of 3Nrrl/min.

At this time, the height of the adhesion of polymer particles to the inner wall of the polymerization vessel is
Table 2 shows the state of the polymer scattered into the monomer recovery piping.

Table 2 Example 3 In Example 1, as the rotating blade on the upper stage of the stirring shaft,
Turbine type (4 blades), Faudler type (3 blades)
, or propeller type (4 blades, blade inclination angle 60°)
Table 3 shows the state of polymer scattering into the polymerized monomer recovery pipe according to the same example except that a cover not shown in Fig. 3 was attached.

Example 4 In Example 1, the upper rotating blade has a diameter (d) of 4
00■, width (b) 50■ using four paddle-shaped blades, deionized water 900Q, partially saponified polyvinyl alcohol 4
0 (200 tons of methylcellulose, 300 JP of 11-fisopropylene dicarbonate), 500 JP of vinyl chloride monomer, and 100 KP of vinyl acetate monomer, and , Polymerization was carried out at a polymerization temperature of 58° C. A reflux (reflux) vdenser was not used during the polymerization.

When the polymerization approached the end and the pressure inside the polymerization vessel decreased to 3 kg/aIG, the polymerization reaction was stopped, and while stirring was continued, unreacted monomers were recovered at a rate of ZNrrl of 1 minute.

Table 4 shows the extent to which the polymer particles adhered to the inner wall and the state of the polymer scattered into the monomer recovery piping.・Table 4

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the heavy-duty device of the present invention; Figures 2 and 3 are
Figures G and 5 show an example of the cover to be installed on the rotary vane for defoaming. Figure 4 is a longitudinal sectional view showing the positional relationship between the rotary vane and the cover that covers it. 1. Main body of heavy container, 2. Rotating shaft. 3. Stirring blade, 4. One rotation blade. 5.5', 5?5", Cover. 6. Reflux condenser, 7 - Drive motor. 8... Pipe, L-Jl phase 1 & blood, F...
foam. Patent Applicant Shinsuke Chemical Industry Co., Ltd. Figure 1 Figure 2 (b) Figure 3 Figure 4 Figure 5 Procedural Amendment 1981 1011 27 ul, i) Indication of 1981 Special #V-No. 147071 No. 3, Relationship with the case to be amended Patent ° Applicant name (206) Shin-Etsu Chemical Co., Ltd. 4, Agent - Address Nagai Building, 4-9 Nihonbashi Honmachi, Chuo-ku, Tokyo 103 [Telephone Tokyo] (270) 011511.08
S 9) ``Spontaneous'' 6. Supplementary lunar elephant ra/d''.

Claims (1)

[Claims] 1. When polymerizing salt 4F, a vinyl monomer, or a monomer mixture mainly consisting of vinyl chloride in an aqueous medium, a rotary blade is provided in the gas phase in the reactor, and By installing a cover over this rotating blade, the bubbles generated on the liquid surface during polymerization and during recovery of unreacted monomer after completion of polymerization are broken by the rotating blade, and the bubbles are scattered due to the broken bubbles. 2.11 A polymerization apparatus consisting of a combiner body, a rotating shaft of a stirring blade material, and a reflux condenser provided as necessary, Polymerization for vinyl chloride, comprising a rotary vane for preventing foaming from the liquid surface above the rotating shaft of the stirring blade material, and a cover for preventing scattering caused by foam breakage on the rotary vane. Device