JP2002114816A - Method and apparatus for removing unreacted vinyl chloride-based monomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both a method for readily dealing with changes of various grades by simple and inexpensive facilities so as to remove an unreacted vinyl chloride-based monomer from a vinyl chloride-based resin slurry and an apparatus therefor. SOLUTION: This method for removing an unreacted vinyl chloride-based monomer comprises continuously introducing a vinyl chloride-based resin slurry containing an unreacted vinyl chloride-based monomer after polymerization to a tank type device in which (1) the inside is divided into an upper and a lower chambers by a perforated plate 1, (2) the upper chamber on the perforated plate is divided by a spiral wall 4 to form a spiral route, (3) a feed opening 5 is arranged on the outer peripheral part of the spiral route, (4) steam is supplied from a steam chamber of the lower chamber through the perforated plate and (5) a draw-out part 6 is installed at the central part of the spiral route, bringing the slurry into contact with steam while passing through the spiral route and removing an unreacted vinyl chloride-based monomer contained in the slurry. This apparatus for the method is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for removing an unreacted monomer by steaming an aqueous suspension (slurry) of a vinyl chloride resin after polymerization containing an unreacted vinyl chloride monomer.

[0002]

2. Description of the Related Art A considerable amount of unreacted vinyl chloride-based monomer remains in an aqueous suspension (slurry) of a vinyl chloride-based resin after polymerization of the vinyl chloride-based monomer in an aqueous suspension. Before these are processed in the subsequent dehydration and drying steps,
It is necessary to perform demonomer treatment.

[0003] For this reason, a number of methods have been proposed in which a vinyl chloride resin slurry is subjected to steam treatment to continuously remove monomers. For example, in Japanese Patent Application Laid-Open No. 54-8693,
There is a method in which a tray column is used and the structure of the tray uses a series of groove-shaped channels, and the monomer is removed in a short time. The method of using such a tray has an advantage that the steam efficiency is good especially in the case of large-scale processing. However, since shelves are used, usually five or more shelves are stacked and used, but they become higher in the height direction. Therefore, a tall maintenance stage is required at the time of inspection of each stage, and the inconvenience of elevating and lowering occurs each time inspection is performed. In addition, since complicated internal structures are stacked for each stage, equipment costs including stage costs are high. Also, unlike the conventional large-scale processing of a single product, when the production of small-volume multi-products increases as in recent years, it becomes necessary to use the same demonomerization equipment to process multiple products. Therefore, it is necessary to cope with the change in the flow rate and the required residence time of the demonomerization condition for each product type.

[0004] It is difficult to carry out this in a conventional multi-stage column made for large-scale processing of a single variety. For example, in the case of a 10-stage column, the column can be used in 9 columns, or 8 columns, 7 columns, or 6 columns. Although it is necessary to switch between the stages and use it, supply equipment is required by that number, and time and energy are lost in cleaning and the switching, and this is not easy.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a demonstrating method and equipment which can easily cope with various condition changes of a small quantity and various kinds with simple equipment of a tank type without using a column tower and which is easy and inexpensive equipment cost. Things.

[0006]

That is, the present invention provides: 1. An aqueous suspension of a vinyl chloride resin after polymerization containing an unreacted vinyl chloride monomer, (1) the inside of which is vertically (2) partitioning the upper plate with a spirally formed wall on the perforated plate to form a spiral passage, (3) providing a supply port on the outer periphery of the spiral passage, (4) steam in the lower chamber Through the perforated plate from the chamber to supply steam,
(5) With a draw-out section in the center of the spiral passage, using a tank-type device, from the supply port provided in the upper chamber, the aqueous suspension is introduced continuously, the aqueous suspension is A method of removing unreacted vinyl chloride-based monomer contained in the aqueous suspension by contacting with water vapor supplied from a lower steam chamber through holes in a perforated plate while passing through the spiral passage (claim) Item 1), 2. The method for removing unreacted vinyl chloride-based monomer according to Item 1, wherein the spirally formed wall is provided substantially perpendicular to the perforated plate (Claim 2). 3. The method for removing unreacted vinyl chloride monomers according to claim 1 or 2, wherein the residence time (residence amount) is controlled by the level of the liquid surface of the aqueous suspension on the spiral passage. ), 4. 4. The method for removing unreacted vinyl chloride-based monomer according to claim 1, wherein the spiral passage and the upper space of the upper room are washed with water by a washing pipe installed along the spiral passage in the upper room. Item 4), 5. An apparatus for continuously demonomerizing an aqueous suspension of a vinyl chloride resin after polymerization containing an unreacted vinyl chloride monomer by steaming, wherein the apparatus is (1)
The inside is vertically divided by a perforated plate, (2) the perforated plate of the upper chamber is partitioned by a wall formed in a spiral shape, a spiral passage is formed, and (3) a supply port is provided on an outer peripheral portion of the spiral passage, (4) A tank type unreacted vinyl chloride monomer, characterized in that steam is supplied from a lower steam chamber through a perforated plate, and (5) a draw-out section is provided at the center of the spiral passage. 5. removal device; 6. The apparatus for removing unreacted vinyl chloride-based monomer according to claim 5, wherein the spirally formed wall is provided substantially perpendicular to the perforated plate. 7. The apparatus for removing unreacted vinyl chloride-based monomers according to claim 5 or 6, wherein the residence time (residence amount) is controlled by the level of the liquid surface of the aqueous suspension. 8. The method for removing unreacted vinyl chloride-based monomer according to claim 5, 6, or 7, wherein the spiral passage and the upper space of the upper room are washed with water by a washing pipe installed along the spiral passage of the upper room. Item 8).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method and apparatus of the present invention comprises dispersing a vinyl chloride-based monomer in an aqueous medium to prepare a polymerized aqueous dispersion (slurry) of a vinyl chloride-based resin produced by a suspension polymerization method. It is widely applied to a method of obtaining a vinyl chloride resin by post-treatment, and is not particularly limited.

Recently, the variety of vinyl chloride products has increased, and accordingly, the variety of small-volume production has also increased. Many of these varieties are special, and the processing conditions are different from those that are easy to demonomerize to those that are difficult to demonstrate, and those that have high heat tolerance in steam treatment, and those that are small, so that these conditions can be changed frequently and smoothly. Without it, it is difficult to supply cheap products to the market.

For such small-quantity, multi-product processing, the conventional tray-type column equipment which prioritizes efficiency in large-scale processing is not always optimal. In other words, a facility that prioritizes that it is easy to change the type or change the processing conditions is suitable. As a result of study based on this idea, we arrived at a simple and small tank-type facility. Changing the liquid level, cleaning, switching, and inspection are all easy with a single tank. For example, compared to equipment with two or more stages, only one operation is required and the number of equipment is less than half the number of two or more stages , Operation and inspection. However, in order to carry out demonomerization in a tank system, it is necessary to take measures to prevent mixing of a slurry having a high monomer concentration near the slurry supply port and a slurry having a low monomer concentration which has been demonomerized near the slurry discharge port. As a result of intensive studies to solve this, the upper chamber into which the slurry enters is partitioned by a single spiral wall, and slurry supply is performed from one end of the spiral, and extraction of the demonomerized slurry is performed from the opposite end. That was solved. Also, if the outlet for water vapor and monomer vapor in the space above the slurry is near the slurry supply side of the upper lid where the slurry enters, the flow of vapor will be from the slurry discharge port with low monomer concentration to the slurry supply port. Since it flows along the spiral in the vicinity of the higher monomer concentration, a decrease in the monomer removing effect can be suppressed, which is advantageous.

[0010] The height of the spiral wall must be at least as high as the liquid height of the slurry from the horizontal porous plate surface of the upper chamber in which the slurry enters, and the upper limit can be appropriately selected as far as it comes into contact with the upper lid. When it is desired to remove the monomer to the concentration, it is needless to say that it is most preferable to select the upper limit wall height for completely spiral partitioning up to the vapor space above the slurry.

The residence time of the slurry, which is most important for demonomerization, in the tank can be set very easily by the tank type. The residence time can be calculated by dividing the slurry retention amount in the tank by the slurry supply amount. When the slurry supply amount is a predetermined value, the necessary slurry retention amount can be obtained by multiplying this by the required residence time. The amount of retained slurry in the tank may be measured with a measuring instrument such as a liquid level gauge, and the liquid level may be changed to maintain a predetermined amount. In other words, the residence time in the tank can be freely adjusted to a predetermined amount, such as by changing the liquid height by measuring the amount of slurry retained by a measuring instrument such as a liquid level gauge, and adjusting the amount of slurry supplied to the tank. Setting can be made very easily. In the case where the processing amount and the required residence time are different for each type, an apparatus which can be easily adjusted in this way is very effective. There are various methods for adjusting the amount of residence using a measuring device for the amount of slurry, and any of them may be employed. The most general type uses a liquid level gauge. For example, the pressure generated with the height of the liquid in the upper chamber where the slurry in the upper chamber is collected is detected, and the height of the liquid is measured from this. The amount of slurry retained in the upper chamber is known by integrating the horizontal surface area and calculating the volume. In addition, any of liquid level detection by a capacitance type and liquid level detection by a radiation irradiation type may be used. Regarding the method of adjusting the residence time by measuring the residence amount, a predetermined residence time can be set by using a device for adjusting the residence amount of the slurry and a device for adjusting the slurry supply amount in combination. There are various methods, and any method may be used. For example, the slurry supply amount is maintained at a predetermined amount by using a combination of a flow meter, a flow control valve, and a control device. The amount of retained slurry is calculated from the required residence time and the amount of slurry supply.However, by detecting the retained amount using a liquid level gauge, by combining a valve for adjusting the amount of slurry withdrawn from the tank and a device for adjusting the amount of slurry. This retention amount can be maintained at a constant predetermined amount.

In a generally employed multi-stage column, the amount of residence in each stage is such that a barrier plate of a certain height is provided at the slurry outlet of each stage, and the liquid is discharged by overflowing the plate. Because it is constant. The amount of retained slurry is a constant amount represented by the product of the height of the weir plate and the sectional area of the column. Therefore, the method of changing the residence time can only be changed by changing the processing flow rate or the number of stages to be used, and has a large restriction.

With respect to the washing of the slurry chamber, in the tank type, the amount of staying in the tank can be freely changed, so that the amount of staying slurry can be quickly reduced to near the sky, washing water is supplied, and washing along the spiral is performed. Water can be washed in a short time by flowing water from a pipe and a watering nozzle attached to the pipe. On the other hand, in the washing in the tray tower, the barrier is provided as described above to maintain the retention amount, so that each stage cannot be emptied due to the structure, and the washing is performed while diluting with a large amount of washing water. . That is, a large amount of cleaning water and a long time are required for cleaning. In the case of the tank type, washing in one tank is sufficient, but washing and washing equipment for the number of stages in a multi-stage tower are required.

[0014] The cleaning pipe may be attached to the lower steam blowing chamber as needed. The spiral structure is also shown as cylindrical in the figure, but it may have corners,
Extremely speaking, a square spiral along a square may be used in a square tube, but it goes without saying that a circle is preferable from the viewpoint of smoothness of flow.

Another advantage of the tank type as compared with the multistage type is that there are fewer restrictions on the installation location of the apparatus.
Since multiple stages require height, they cannot be installed in places with restrictions in the height direction. On the other hand, since the tank type equipment is compact, there are very few restrictions on the installation location.

The demonomer blows water vapor into the lower chamber, and the water vapor passes through a horizontal perforated plate which separates the upper and lower parts, enters the slurry in the upper chamber, and flows out of the slurry upward in a bubble state. This is done by incorporating the monomers into the vapor. Since the water vapor containing this monomer accumulates in the upper space partitioned by the spiral wall, an exhaust port is provided in the upper lid of the upper chamber and discharged. This exhaust port is preferably provided near the slurry supply port, that is, near the place where the monomer concentration in the slurry is high. In this case, since the inside of the spiral wall is exhausted from the lower monomer concentration to the higher monomer concentration, the efficiency of demonomerization is high. The vinyl chloride resin slurry is obtained by suspending a vinyl chloride monomer in an aqueous medium using a suspending agent, and performing suspension polymerization at a constant temperature using an oil-soluble polymerization initiator. If the pressure of the monomer itself is high, the unreacted vinyl chloride monomer remaining after the polymerization is recovered using the pressure, and after the pressure is reduced to about atmospheric pressure, a vacuum pump or the like is used. Collect under reduced pressure. The amount of unreacted vinyl chloride monomer recovered by these methods is limited, and usually tens of thousands of p
pm to about 200 ppm. The vinyl chloride-based monomer is a monomer mixture composed of vinyl chloride alone or another monomer copolymerizable with vinyl chloride. Other monomers that can be copolymerized with vinyl chloride are monomers such as ethylene, propylene, vinyl acetate, allyl chloride and the like, and these are used alone or in combination of two or more.

[0017]

EXAMPLES (Production of vinyl chloride resin slurry) A: Pure water 5800Kg a pressure vessel equipped with a suspension for stirring blades 10M ^3, the polymerization initiator di-2-ethylhexyl Pas - Okishijika - BONNET - DOO 650g 3500 cc of a mineral spirit solution in which 650 g of t-butyl peroxyneodecaneate and 650 g of t-butyl peroxyneodecane were dissolved, and 1890 partially saponified polyvinyl acetate
126L of an aqueous solution in which g
After adding 100 kg, the temperature was raised to 55 ° C., polymerization was carried out for about 4 hours with stirring, and when the pressure in the vessel began to decrease, the vinyl chloride monomer was recovered. An aqueous suspension (polymerization degree 1000) was obtained. B: pure water in a pressure vessel equipped with a suspension for a stirring blade 10M ³ 5800Kg, the polymerization initiator di-2-ethylhexyl Pas - Okishijika - BONNET - DOO 520g and t- Buchirupa - Okishineodekane - minerals dissolved preparative 520g Spirit solution 2800cc, partially saponified polyvinyl acetate 1890
126L of an aqueous solution in which g
After adding 100 kg, the temperature was raised to 62 ° C., polymerization was carried out for about 4 hours with stirring, and when the pressure in the vessel began to drop, the vinyl chloride monomer was recovered, and the polymerization was completed in 5 hours. An aqueous suspension (degree of polymerization 800) was obtained. (Example 1) An upper chamber for supplying slurry in a cylindrical shape having an inner diameter of 1700 mm and a width of about 200 mm and a height of 1600 m
m, using a tank-type equipment shown in FIG. 1 consisting of a perforated plate having an opening ratio of 1.0% and a hole diameter of 1.4 mm. Used in the flow shown in FIG. The remaining monomer in the vinyl chloride resin (polymerization degree: 800) was supplied at 200 ppm at 6.6 m ³ / h from the outer edge of the spiral and extracted from the center of the spiral. For extracting the slurry, the liquid level is detected using a differential pressure transmission type liquid level gauge attached to the liquid level attached to the tank wall.
The method was carried out by controlling a flow control valve attached to the slurry extraction pipe so that the liquid height was 1000 mm. By keeping the liquid height at 1000 mm, the slurry stayed in the tank for 20 minutes from the tank inlet to the tank outlet. The temperature in the tank was 100 ° C. by the steam treatment. The residual monomer in the extracted slurry was reduced to 1 ppm.
Next, the slurry supply flow rate was changed to 4.6 m ³ / h.
The liquid level was detected by a liquid level gauge, and the slurry was extracted by controlling the flow rate control valve so that the amount of the extracted slurry became 700 mm. By keeping the liquid height at 700 mm, the residence time of the slurry in the tank became 20 minutes. The temperature in the tank is 10
It was 0 ° C. The residual monomer in the slurry was 200 ppm in the resin at the time of supply, but the residual monomer in the resin extracted from the tank was 0.8 ppm. As described above, the adjustment for securing the residence time in accordance with the change in the slurry supply amount was very easily performed only by changing the set value of the height of the liquid level gauge. (Example 2) Vinyl chloride resin (800 degree of polymerization) with the equipment shown in Example 1 and the flow shown in FIG. 2 as in Example 1.
6.6 m ³ / h of the remaining monomer in 200 ppm
And the slurry was retained at 100 ° C. for 20 minutes and extracted from the center of the spiral. As a result, the residual monomer in the slurry was reduced to 1 ppm. The height of the slurry liquid at this time was 1000 mm. Subsequently, slurry of different types (polymerization degree: 1000 products) was flowed at 6.6 m ³ /
h. Since the required residence time of this product was 11 minutes, the liquid height was reduced to 550 mm by a liquid level meter, and the residence time was adjusted to 11 minutes. The residual monomer of this resin was 300 ppm in the original slurry and 0.8 ppm in the resin extracted after the steam treatment. Changing the residence time was easy only by changing the set value of the liquid level gauge. The liquid level meter for measuring the amount of the slurry was carried out by using a differential pressure transmitter based on the liquid height and adjusting the amount of the slurry to be withdrawn so as to maintain a constant liquid amount.

Example 3 A vinyl chloride resin slurry was treated at a liquid height of 1000 mm and 6.6 m ³ / h with the same equipment as in Example 1 and the flow shown in FIG.
Slurry extraction cleaning was performed. The supply of the slurry was stopped, the water was switched to the cleaning water, and the liquid height was reduced to about 50 mm, so that the cleaning time was 20 minutes and almost no slurry was obtained. The washing water used was 2 m ³ .

(Embodiment 4) To see the effect of the tank type spiral
Upper chamber for supplying slurry in a cylindrical shape with an inner diameter of 400 mm
Is a 1600mm high spiral with a width of about 50mm
The partition between the steam in the lower chamber and the opening ratio
It is shown in FIG. 1 consisting of a perforated plate with a hole diameter of 1.4 mm at 1.0%.
Use the tank type equipment of the structure and use it in the flow shown in FIG.
Was. Residual monomer in vinyl chloride resin (polymerization degree 800)
ー is 200ppm 0.4m ^Three/ H spiral
Spy at 100 ° C for 20 minutes
The slurry extracted from the center of the ral
It dropped to 1 ppm. The slurry liquid height at this time is 106
It was 0 mm.

(Embodiment 5) In the apparatus of Embodiment 1, a washing water pipe for washing the slurry scattered and attached to the space above the slurry at required time intervals was provided along the spiral wall. Small holes were formed in the pipe evenly in the circumferential direction of the pipe so that the washing water washed the space.

The pipe was divided into four parts in the length direction so that the supply of washing water could be supplied from four locations, and the number of washings, the washing time, and the amount of washing water were determined according to the necessity of washing.

The cleaning condition was observed from a viewing window provided on the upper lid.

(Comparative Example 1) For the sake of comparison, the same slurry was flowed at the same flow rate of 0.4 m ³ / h and the liquid height was set to 1 using the same equipment as in Example 4 and using a tank from which only the internal spiral wall was removed.
At 060 mm, the residence time was 20 minutes. The residual monomer in the vinyl chloride resin (polymerization degree: 800) was 200 ppm, and the residual monomer in the extracted resin was 70 ppm. The effect of improving the removal rate by the spiral was apparent.

[0024]

According to the present invention, the continuous vinyl chloride-based monomer removing apparatus by steam treatment is of a tank type, the inside of which is vertically divided by a horizontal perforated plate, and the upper chamber on the perforated plate in which the slurry enters is a series of spirals. Provided is a method consisting of simple equipment separated by vertical walls, making it possible to extremely easily change the amount of retained slurry, and to facilitate the change of monomer removal conditions necessary for the processing of various types and the type change.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of the structure of a tank-type device having a spiral wall according to the present invention.

FIG. 2 is a conceptual diagram showing a state of demonomerization treatment using the method and the apparatus of Example 1 of the present invention.

FIG. 3 is a conceptual diagram showing a state of a demonomerization treatment using a method and an apparatus of Comparative Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Perforated plate 2 Upper chamber 3 Lower chamber 4 Spiral wall 5 Slurry supply port 6 Slurry extraction port 7 Exhaust port 8 Water vapor blowing port 9 Liquid level gauge 10 Top lid 11 Rinse pipe 12 Rinse nozzle 13 Slurry tank 14 Slurry supply pump 15 Column tower 16 Steam blow-in pipe 17 Slurry extraction pump 18 Condenser 19 Vacuum pump 20 Slurry supply port 21 Exhaust port 22 Liquid level gauge 23 Flow control valve 24 Tank type spiral residual VCM removal device

Claims (8)

[Claims] 1. A vinyl chloride resin slurry after polymerization containing an unreacted vinyl chloride monomer is (1) partitioned into upper and lower parts by a perforated plate, and (2) formed on the perforated plate of the upper chamber in a spiral shape. (3) A supply port is provided in the outer periphery of the spiral passage, (4) Steam is supplied from a lower steam chamber through a perforated plate, and (5) ) Using a tank-type device provided with a draw-out portion at the center of the spiral passage, the vinyl chloride resin slurry was continuously introduced from a supply port provided in the upper chamber, and the slurry passed through the spiral passage. A method of removing unreacted vinyl chloride-based monomer contained in the slurry by bringing the slurry into contact with steam supplied from a lower steam chamber through a hole in a perforated plate. 2. The method for removing unreacted vinyl chloride-based monomer according to claim 1, wherein the spirally formed wall is provided substantially perpendicular to the perforated plate. 3. The method for removing unreacted vinyl chloride-based monomer according to claim 1, wherein the residence time (residence amount) is controlled by the height of the slurry liquid level on the spiral passage. 4. The unreacted vinyl chloride monomer according to claim 1, 2 or 3, wherein the spiral passage and the upper space of the upper chamber are washed with water by a washing pipe installed along the spiral passage of the upper chamber. How to remove. 5. An apparatus for continuously demonomerizing a polymerized vinyl chloride resin slurry containing an unreacted vinyl chloride monomer by steaming, wherein the apparatus has (1) a porous inside. (2) partitioning the porous plate of the upper chamber with a wall formed in a spiral shape to form a spiral passage, (3) providing a supply port in the outer periphery of the spiral passage, (4) (5) A tank-type unreacted vinyl chloride-based monomer removing device, characterized in that steam is supplied from a lower steam chamber through a perforated plate, and a draw-out portion is provided at the center of the spiral passage. 6. The apparatus for removing unreacted vinyl chloride-based monomers according to claim 5, wherein the spirally formed wall is provided substantially perpendicular to the perforated plate. 7. The apparatus for removing unreacted vinyl chloride-based monomer according to claim 5, wherein the residence time (residence amount) is controlled by the height of the liquid surface of the vinyl chloride-based resin slurry. 8. The unreacted vinyl chloride-based monomer according to claim 5, 6 or 7, wherein the spiral passage and the upper space of the upper room are washed with water by a washing pipe installed along the spiral passage of the upper room. How to remove.