KR20030042170A - Non-reacted monomer collection system for vinyl chloride based paste resin - Google Patents

Abstract

PURPOSE: Provided is a device for recovery of unreacted monomers, which can recover unreacted monomers from paste resin latex based on vinyl chloride, in high efficiency. CONSTITUTION: The device comprises an evaporation column set to reduced pressure condition; a feed line for supplying a paste resin latex based on vinyl chloride to the evaporation column, which is connected to the top of the evaporation column; a indirect heat exchanger(6) for heating a latex at the inside of the feed line by heat exchange of latex and hot water; a spray nozzle(12) for spraying the fed latex to the inside of the evaporation column; a gas vent line(14) for discharging a reactant containing unreacted monomer-containing gas and latex bubble; and a rotating bubble separator(24) for removing bubbles from the reactant, which comprises a impeller body rotating by a driving shaft, and a plurality of tubes.

Description

Non-reacted monomer recovery apparatus of vinyl chloride paste resin latex {NON-REACTED MONOMER COLLECTION SYSTEM FOR VINYL CHLORIDE BASED PASTE RESIN}

The present invention relates to an unreacted monomer recovery apparatus for vinyl chloride paste resin latex, and more particularly, to provide stable continuous operation by providing an indirect heat exchanger for latex heating and a highly efficient rotary bubble separator for removing the reactant bubbles. It relates to an unreacted monomer recovery apparatus that makes it possible.

In general, the suspension polymerization method used for the production of vinyl chloride resin is an aqueous medium dispersant and a polymerization initiator in a vinyl chloride monomer, and the emulsion polymerization method is an inside of a polymerizer in which an emulsifier and a polymerization initiator are added to a vinyl chloride monomer. It is made to stir while maintaining a constant temperature in the polymerization.

The polymerization reaction is stopped at a stage where the polymerization reaction rate of the vinyl chloride monomer reaches approximately 80 to 95%, and since the vinyl chloride paste resin in the polymerizer contains several% of unreacted monomer after the completion of the polymerization reaction, the chloride It is essential to remove and recover the unreacted monomer from the vinyl paste resin.

Usually, polyvinyl chloride-based resin having an average particle diameter of 100 to 200 µm is prepared by suspension polymerization, and the property after completion of polymerization is slurry. It is known to use a multistage stripping column having a porous plate as a method for recovering the unreacted monomer from such a slurry-like vinyl chloride resin.

Here, the stripping column is an apparatus designed so that the flow direction of the polymer solution including the solvent to be recovered and the flow direction of steam providing heat required for recovery are opposite to each other.

On the other hand, vinyl chloride resins having an average particle diameter of about 1 µm are produced by emulsion polymerization method or fine suspension polymerization method, and the properties after completion of polymerization are latex phase. However, the latex phase has an unreacted monomer recovery apparatus in which two or more bubble separators 3 are installed in parallel with the multi-stage stripping column 1 in consideration of many bubbles generated in comparison with the slurry phase. Proposed.

The recovery device supplies latex to the uppermost porous plate 1a of the stripping column 1 through the treatment liquid supply line 5 and the lowermost porous plate 1b of the stripping column 1 through the steam supply line 7. ) By supplying steam, and separating the unreacted monomer by gas-liquid contact by bubbling generated inside the stripping column (1) to recover through the gas discharge line (9). At this time, the two bubble separators 3 selectively switch over by the control means (not shown) to remove bubbles of the reactants.

However, latex vinyl chloride-based resin is poor in stability, and latex stagnates in the lower part of the stripping column (1), which easily deteriorates, and the porous plate is frequently blocked by latex, requiring frequent cleaning of the equipment. It does not have a lot of solids, so there is a big disadvantage of energy loss during product drying.

In addition, under reduced pressure conditions, since latex generates a very large amount of bubbles exceeding the processing capacity of conventionally known bubble separators, it is difficult to deal with a large amount of bubbles generated in latex with a known bubble separator. There is.

As a result, methods and apparatuses for recovering unreacted monomers suitable for the characteristics of latex vinyl chloride-based resins have been proposed. Among them, a method of evaporating and recovering unreacted monomers by heating a latex stored in a reduced pressure recovery apparatus in a batch method is known.

4 is a schematic view of a batch unreacted monomer recovery apparatus according to the prior art, wherein the recovery apparatus supplies the treated vinyl chloride-based resin latex to the reduced pressure recovery tank 13 through the treatment liquid supply line 11 and supplies steam. The steam provided through the line 15 is directly injected into the latex inside the decompression tank 13 through the steam eject 17 to raise the latex temperature.

At this time, hot water is supplied into the jacket 21 for raising the temperature through the jacket hot water line 19 to maintain a constant temperature of the pressure reduction recovery tank 13. When the temperature of the latex rises by the steam, the latex The unreacted monomer is evaporated from, and the evaporated unreacted monomer is recovered through the gas discharge line 23, and the vinyl chloride-based resin latex from which the monomer is removed through the above process is processed through the process liquid discharge line 25. Is transferred to.

However, the recovery device has a disadvantage that the unreacted monomer treatment is performed in a single step rather than in a continuous manner, and continuous operation is difficult due to frequent clogging of the steam eject 17 by latex even when the device is continuously operated. In addition, since a lot of bubbles are generated due to the nature of the latex so that a large amount of bubbles are passed to the gas discharge line 23, it is not possible to increase the degree of vacuum inside the reduced pressure recovery tank 13, the recovery rate of the unreacted monomer is lowered, the recovery time is increased There is a limit.

As a result, even when a defoamer or a conventional bubble separator is used to remove the bubbles of the reactants, as described above, since the latex generates a very large amount of bubbles exceeding the processing capacity of the known bubble separators, the bubbles are generated in the gas discharge line ( I have the problem that goes to 23).

Therefore, the present invention is to solve the above problems, the object of the present invention is to realize a latex heating and unreacted monomer removal through a stable continuous operation, having a high-efficiency bubble separator so that bubbles do not flow to the gas discharge line To provide an unreacted monomer recovery apparatus capable of recovering unreacted monomers from vinyl chloride paste resin latex with high efficiency.

1 is a schematic view of an unreacted monomer recovery apparatus according to the present invention.

2 is a partially enlarged view of a rotary bubble separator according to the present invention.

3 and 4 are schematic views of an unreacted monomer recovery apparatus according to the prior art, respectively.

* Description of the main parts of the drawings * 2: Evaporation column 4: Treatment liquid supply line

6: indirect heat exchanger 12: spray nozzle

14 gas discharge line 16 treatment liquid circulation line

18: treatment liquid discharge line 24: rotary bubble separator

26: drain port 32: drive shaft

34 impeller body 36 fixed tube

38: extension tube 40: gas outlet

In order to achieve the above object, the present invention,

An evaporation column set under a reduced pressure condition, a treatment liquid supply line connected to an upper end of the evaporation column, and supplying a vinyl chloride paste resin latex from which a polymerization reaction is completed to an evaporation column, and provided to the treatment liquid supply line to provide latex and hot water. An indirect heat exchanger for heating the latex inside the treatment liquid supply line through heat exchange of the spray nozzle, a spray nozzle for injecting the latex provided between the treatment liquid supply line and the evaporation column into the evaporation column, and a top of the evaporation column. A vinyl chloride paste resin including a gas discharge line provided to discharge a reactant including an unreacted monomer-containing gas and a latex bubble in an evaporation column, and a rotary bubble separator provided to the gas discharge line to remove bubbles from the reactant Provided is an unreacted monomer recovery apparatus for latex.

Preferably, the rotary bubble separator is a drive shaft for rotating the power received from the drive motor to form a gas outlet therein, an impeller body assembled to one end of the drive shaft, a plurality of fixed tubes detachably installed on the impeller body and It consists of a plurality of extension tube is installed to extend the length adjustable from the fixed tube.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic diagram of an unreacted monomer recovery apparatus according to an embodiment of the present invention, wherein the recovery apparatus includes an evaporation column (2) set under reduced pressure conditions and a vinyl chloride-based polymerization reaction in the evaporation column (2). A treatment liquid supply line 4 for supplying a paste resin latex (hereinafter referred to as a latex for convenience) and an indirect heat exchanger 6 provided in the treatment liquid supply line 4 to heat the latex by heat exchange between hot water and latex. It is provided.

The indirect heat exchanger 6 raises the temperature of the latex by heat exchange between the hot water and the latex, unlike the known steam ejection, which injects steam directly into the latex.

That is, the indirect heat exchanger (6) receives the hot water of 80 ~ 90 ℃ stored in the hot water storage tank (8) through the pump 10, the latex inside the treatment liquid supply line (4) by the heat exchange between the latex and hot water Heated to 60-80 ° C. The heated latex is provided inside the evaporation column 2, and the hot water used for latex heating is circulated to the hot water storage tank 8 and reused for latex heating.

As described above, the indirect heat exchanger 6 that heats the latex by heat exchange between the latex and the hot water has no clogging caused by the latex and thus can be continuously operated for a long time. It has the advantage of preventing the degradation phenomenon.

The recovery device includes a spray nozzle 12 which is connected to the end of the treatment liquid supply line 4 and sprays the latex provided into the evaporation column 2, and is provided on the evaporation column 2 to provide an unreacted monomer-containing gas. Next, a process liquid circulation line 16 provided between the gas discharge line 14 for discharging, the lower end of the evaporation column 2 and the process liquid supply line 4 to circulate the latex, and the latex from which the unreacted monomer is removed are next. The treatment liquid discharge line 18 which discharges to a process is provided.

The spray nozzle 12 sprays the supplied latex in the form of a fog, thereby increasing the surface area of the latex particles to improve the evaporation efficiency of the unreacted monomer. When the latex is injected through the spray nozzle 12 as described above, an unreacted monomer-containing gas is generated while the unreacted monomer contained in the latex is evaporated. 2) Goes to the bottom.

At this time, the treatment liquid circulation line 16 and the treatment liquid discharge line 18 are provided with respective first and second valves 20 and 22, and the first valve 20 is opened in the latex circulation process. The process liquid circulation line 16 is opened, and after a predetermined time, the process liquid circulation process is continued and the second valve 22 is opened in the process of transferring the latex from which the unreacted monomers are removed to the next process. The treatment liquid discharge line 18 is opened.

In the process of circulating the latex through the treatment liquid circulation line 16 as described above, the unreacted monomer-containing gas generated in the evaporation column 2 is discharged through the gas discharge line 14 to be recovered. Since a large amount of bubbles are generated inside the evaporation column 2, the bubbles are discharged to the gas discharge line 14 together with the unreacted monomer-containing gas.

Therefore, the recovery device according to the present embodiment is provided between the rotary bubble separator 24 and the rotary bubble separator 24 and the evaporation column 2 which are provided in the gas discharge line 14 to remove the bubbles contained in the reactants with high efficiency. Maintains a constant pressure inside the evaporation column (2) provided with a drain port (26) provided, a third valve (30) provided in the vacuum pump connection line (28) and interlocked with the rotary bubble separator (24). The fourth valve 31 is provided.

The rotary bubble separator 24 is designed to be highly efficient so as to be suitable for continuous processing of a very large amount of bubbles generated in latex, and FIG. 2 shows a part of the rotary bubble separator according to the present embodiment.

The rotary bubble separator 24 includes a driving shaft 32 that receives power from a driving motor (not shown), an impeller body 34 assembled to one end of the driving shaft 32, and a plurality of impeller bodies 34. And a gas discharge port 40 for discharging the unreacted monomer-containing gas separated from the bubbles by the rotation of the impeller body 34.

In particular, the fixed tube 36 is detachably installed on the impeller body 34 to easily adjust the number of fixed tubes 36 installed on the impeller body 34, and the extension tube 38 is fixed tube 36. Length can be adjusted.

As a result, the number of the fixed tubes 36 and the length of the extension tubes 38 are adjusted according to the state of the bubbles supplied to the rotary bubble separator 24 to facilitate the centrifugal force applied to the reactants by the rotation of the impeller body 34. Has the advantage of being adjusted.

Accordingly, when the reactant including the unreacted monomer-containing gas and latex bubbles is supplied to the rotary bubble separator 24 in the evaporation column 2, the fixed tube 36 and the extension tube 38 are driven at a high speed about the impeller body 34. While rotating, the centrifugal force is applied to the reaction.

As a result of this, the reactant collects light weight gas into the center of the impeller body 34 by centrifugal force, and moves to the gas outlet 40 through the inside of the drive shaft 32, and the heavy weight latex is extended through the tube 38 The liquid latex is agglomerated to the bottom of the rotary bubble separator 24. On the other hand, the liquid latex aggregated at the lower end of the rotary bubble separator 24 is recovered to the evaporation column 2 through the drain port 26 shown in FIG.

As such, the rotary bubble separator 24 effectively separates the latex component and the unreacted monomer-containing gas while removing bubbles from the reactants.

The rotary bubble separator 24 having the above-described configuration does not cause clogging of the bubble separator itself during operation, thus enabling continuous operation, and having excellent bubble separation performance, as bubbles do not flow into the vacuum pump connection line 28. In addition, the degree of vacuum inside the evaporation column 2 can be maintained at a high level, thereby enabling high-efficiency unreacted monomer recovery.

In addition, the rotary bubble separator 24 can adjust the number of the fixed tube 36 and the length of the extension tube 38 according to the operating conditions of the evaporation column 2, and can flexibly cope with changes in the operating conditions.

In addition, when the driving motor of the bubble separator 24 exceeds the predetermined load and the operation stops, the control unit 42 transmits a control signal to the third valve 30 to block the vacuum pump connection line 28 so that the latex bubble is released. Do not pass through the vacuum pump connection line (28).

EXAMPLE

Hereinafter, this invention is demonstrated concretely using an Example and a comparative example, and the measurement evaluation in the said Example and the comparative example was performed by the following method.

The evaporation column (2) was used with a diameter of 2,000 mm and a height of 8,000 mm, the latex was heated by an indirect heat exchanger (6), and a rotary bubble separator between the top of the evaporation column (2) and the vacuum pump connection line (28). (24) was installed. Then, the sight glass was installed at the rear end of the rotary bubble separator 24, and the operation was performed while observing whether the bubble passed to the vacuum pump connection line 28. The quality of the vinyl chloride resin was compared to the characteristics of the product by processing the dry product after the recovery of unreacted monomer.

[Measurement Method of Unreacted Monomer]

Evaluation of the residual monomer concentration in vinyl chloride paste resin was measured by the head space method using gas chromatography HP-5890 (brand name). That is, 2 g of vinyl chloride paste latex was weighed and the concentration of unreacted vinyl chloride in the ppm range was measured. The conditions were in accordance with D4443 of the ASTM method.

[Sol color measurement method]

The sample containing the plasticizer in the product was mixed with a high-speed mixer (this state is called a sol state), and the bubbles contained in the sol were removed and a sol color (model name: MINOLTA, CR200) was used. White index) was measured. The white index of the color measuring instrument is defined by the following formula, and the L, a, b values of the measurement sample were measured twice and averaged.

White index (WI) = (L × L- (b × 5.7)) / 100) -4

(Example 1)

The vinyl chloride monomer and the aqueous medium were emulsion polymerized in a polymerization reactor to obtain a paste resin latex having an average particle diameter of 1 µm and a latex concentration of 50% by weight. The residual monomer concentration in the vinyl chloride paste resin at this time was 15,000 ppm with respect to the latex weight.

The obtained latex was supplied to the evaporation column 2 shown in FIG. 1 at a temperature of 60 ° C. and a flow rate of 8 m ³ / Hr, the residence time of the latex evaporation column 2 was 60 minutes, and the circulating latex flow rate was 8 m ^3. / Hr, the pressure inside the evaporation column (2) was -0.5kg / cm ² . In addition, the rotary bubble separator 24 installed in the gas discharge line 14 was operated, and the vinyl chloride paste resin latex accumulated in the rotary bubble separator 24 was returned to the evaporation column. The residual monomer concentration of the obtained vinyl chloride paste resin was good at 1,000 ppm.

(Example 2)

Latex at 75 ° C. was supplied to the evaporation column 2 at a flow rate of 8 m ³ / Hr, the residence time of the latex evaporation column 2 was 60 minutes, the circulating latex flow rate was 15 m ³ / Hr, and the pressure inside the evaporation column. Was -0.5 kg / cm ² , except that this was carried out in the same manner as in Example 1. Bubbles did not flow into the vacuum pump connection line 28, and continuous processing was possible. The residual monomer concentration of the obtained vinyl chloride paste resin was good at 500 ppm.

(Example 3)

Latex at 80 ° C. was supplied to the evaporation column 2 at a flow rate of 8 m ³ / Hr, the residence time of the latex evaporation column 2 was 60 minutes, the circulating latex flow rate was 25 m ³ / Hr, and the evaporation column 2 The internal pressure was -0.7 kg / cm ² , except that this was performed in the same manner as in Example 1. Bubbles did not flow into the vacuum pump connection line 28, and continuous processing was possible. The residual monomer concentration of the obtained vinyl chloride paste resin was good at 200 ppm.

(Comparative Example 1)

The same process as in Example 1 was carried out except that the rotary bubble separator 24 was not used. A large amount of bubbles passed to the vacuum pump recovery line 28, the operation was stopped due to failure of the vacuum pump.

(Comparative Example 2)

The vinyl chloride paste resin latex was treated using a batch unreacted monomer recovery apparatus shown in FIG. 4. The pressure-sensitive recovery tank 13 having a capacity of 50 m ³ was filled up to 40% with a paste resin latex and operated for 90 minutes under conditions of a treatment temperature of 60 ° C. and a vacuum degree of −0.7 kg / cm ² . The residual monomer concentration of the obtained vinyl chloride paste resin was 2,500 ppm.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Use of rotary bubble separator Rotary O Rotary O Rotary O Rotary O Batch X Latex temperature (℃) 60 75 80 60 60 Operating pressure (kg / cm ² ) -0.5 -0.5 -0.7 -0.5 -0.7 Supply Latex / Circulation Latex Flow (m ³ / Hr) 8/8 8/15 8/25 8/8 - Residual vinyl chloride monomer concentration (ppm) before treatment 15,000 15,000 15,000 15,000 15,000 Residual vinyl chloride monomer concentration (ppm) after treatment 1,000 500 200 - 2,500 Latex concentration before and after treatment (%) 48/48 48/49 48 / 49.5 - 48 / 47.5 Driving time (min) 60 60 60 - 90 Sol color (before / after treatment) 85/85 85/85 85/85 - 85/85

As can be seen from the above table, the unreacted monomer recovery apparatus according to the present invention, which raises the latex temperature by using an indirect heat exchanger and continuously operates by installing a rotary bubble separator, does not cause deterioration in quality and does not deteriorate the vinyl chloride paste. Unreacted monomer can be recovered from the resin latex with high efficiency.

As described above, according to the method and apparatus for recovering unreacted monomers according to the present invention, heating of latex and removal of unreacted monomers can be realized through stable continuous operation, and unreacted while minimizing energy loss by improving bubble separation performance of the bubble separator. The monomer can be recovered with high efficiency.

Claims (8)

An evaporation column set under reduced pressure conditions; A treatment liquid supply line connected to an upper end of the evaporation column to supply a vinyl chloride paste resin latex from which a polymerization reaction is completed, to an evaporation column; An indirect heat exchanger provided to the treatment liquid supply line to heat the latex inside the treatment liquid supply line through heat exchange between the latex and the hot water; a latex provided between the treatment liquid supply line and the evaporation column and supplied into the evaporation column. A spray nozzle for spraying; A gas discharge line provided on the evaporation column to discharge a reactant including an unreacted monomer-containing gas and latex bubbles in the evaporation column; And A rotary bubble separator provided in the gas discharge line, the impeller body rotating by a drive shaft, and a plurality of tubes installed in the impeller body to adjust the number and length of the impeller body to remove bubbles from the reactants; Unreacted monomer recovery apparatus for vinyl chloride paste resin latex comprising a. The method of claim 1, The indirect heat exchanger receives hot water stored in a hot water storage tank through a pump, and hot water used for latex heating is circulated to a hot water storage tank to reuse the vinyl chloride paste resin latex unreacted monomer recovery apparatus. The method of claim 1, A vinyl chloride paste resin latex further comprising a treatment liquid circulation line provided between the bottom of the evaporation column and the treatment liquid supply line to circulate the latex, and a treatment liquid discharge line for transferring the latex from which the unreacted monomer is removed to the next process. Unreacted monomer recovery apparatus. The method of claim 3, wherein Further comprising a first valve provided in the treatment liquid circulation line, and a second valve provided in the treatment liquid discharge line, the latex from which the unreacted monomer is removed by opening the second valve after the treatment liquid circulation line is operated. The unreacted monomer recovery apparatus of vinyl chloride paste resin latex which transfers to the next process. The method of claim 1, The rotary bubble separator, A drive shaft that receives power from the drive motor and rotates and forms a gas outlet therein; An impeller body assembled to one end of the drive shaft; A plurality of fixing tubes detachably installed on the impeller body; And Apparatus for recovering unreacted monomer of vinyl chloride paste resin latex comprising a plurality of extension tubes extending from the fixed tube to be adjustable in length. The method according to claim 1 or 5, And a drain port provided between the rotary bubble separator and the evaporation column to recover the latex aggregated in the rotary bubble separator to the evaporation column. The method according to claim 1 or 5, And a third valve connected to the gas outlet of the drive shaft, and a third valve provided to the vacuum pump connection line to interlock with the rotary bubble separator. The method of claim 7, wherein The control unit is installed between the drive motor and the third valve of the rotary bubble separator, when the drive motor exceeds the set load, the control unit operates the third valve to block the vacuum pump connection line to block the unreacted monomer of vinyl chloride paste resin latex Recovery device.