KR20070047979A - Method for stripping residual monomer in the polymer latex or slurry using ultrasonic wave under vacuum and stripper using the same - Google Patents

Abstract

The present invention discloses a method for removing unreacted monomers by irradiating a polymer containing unreacted monomers under reduced pressure to remove unreacted monomers and volatile substances other than unreacted monomers from the polymer.

The method of removing unreacted monomers of the present invention is possible to maintain excellent quality of products, reduce environmental pollution and reduce costs by removing and recovering unreacted monomers from latex or slurry with excellent efficiency by applying ultrasonic waves under vacuum. .

Unreacted monomer, ultrasonic, degassing, vacuum

Description

Method for stripping residual monomer in the polymer latex or slurry using ultrasonic wave under vacuum and stripper using the same}

1 is a schematic diagram of a vacuum ultrasonic degassing apparatus.

Figure 2 is a graph showing the relative residual unreacted monomer content over time in the examples and comparative examples of the present invention.

<Brief description of the major symbols in the drawings>

1: degassing tank 2: top cover

3: stirring device 4: ultrasonic oscillator

5: heating jacket 6: slurry (or latex)

7 transfer pump 8 input unit

9: drain valve 10: drain pump

11: degassing monomer outlet 12: vacuum pump

The present invention relates to a stripping process for removing unreacted monomers after a polymer polymerization reaction, and more particularly, to a method for removing residual unreacted monomers in a polymer latex or slurry using vacuum ultrasonic oscillation and a removal apparatus using the same. .

In the degassing step after the polymerization reaction, unreacted monomers are usually removed by using hot steam (about 100 to 130 ° C). In the case of the polymer compound in the form of a slurry, steam degassing is performed while the slurry is kept in a hot steam degassing apparatus for a short time (about 5 to 10 minutes). When the particle size of the polymer compound is present in the form of latex, the latex is raised to about 60 ° C. and then sprayed in a degassing apparatus.

When the slurry is steam degassed using hot steam, the slurry partially accumulates in the degassing apparatus to generate foreign substances. Since this causes the deterioration of quality, to solve this problem, there is a problem in that the operation of the degassing apparatus must be stopped and cleaned periodically.

In the case of latex, it is important to maintain the stability of the latex to maintain the quality, so as in the case of slurry PVC (Suspension PVC, hereinafter referred to as S-PVC), it is necessary to use latex using high temperature (over 100 ℃) steam. Since it is impossible to degas while maintaining the temperature at high temperature, it is sprayed after heat exchange (maintaining about 50 to 60 ° C. latex temperature), but the concentration of residual unreacted monomer is several hundred times higher than that of steam degassing. For example, in the case of environmental management standards, the concentration of residual vinyl chloride monomer (hereinafter referred to as RVCM) of S-PVC is about 1 to 99 ppm in the general PVC polymerization process, but is 1000 ppm or more in latex PVC. . If the residual unreacted monomer concentration is high, the polymer compound is dried through high temperature steam spray drying in the post-drying process and the unreacted monomer is volatilized to the air, which adversely affects the environment and causes deterioration of the final product quality such as thermal stability. Becomes Therefore, there is a need for a method capable of significantly lowering the concentration of residual unreacted monomers without destroying latex stability.

Japanese Patent Laid-Open No. 51-047077 discloses a method of removing unreacted monomers from a high molecular compound using ultrasonic waves. In the above method, nitrogen was used as a carrier gas to effectively remove unreacted monomers. In this case, a separation process is required to reuse the degassed unreacted monomers and the carrier gas. However, there is a great difficulty in applying to the actual process in terms of economic efficiency. In addition, in the case of unreacted monomer degassing in latex using ultrasonic waves and carrier gas, there is a problem of bubble generation due to carrier gas inflow.

Therefore, there is a need for a method for effectively removing and recovering unreacted monomer in polymer latex or slurry without using a carrier gas.

The first technical problem to be achieved by the present invention is to provide a method for effectively removing the unreacted monomer from the polymer latex or slurry without using a carrier gas in order to solve the problems of the prior art.

The second technical problem to be achieved by the present invention is to provide a removal apparatus using the removal method.

The present invention to achieve the first technical problem,

An unreacted monomer removal method is provided in which a polymer containing unreacted monomers is irradiated under ultrasonic pressure to remove unreacted monomers and volatiles other than unreacted monomers from the polymer.

According to one embodiment of the invention, in the removal method, the polymer is preferably in the slurry or latex state capable of the progress of the ultrasonic wave.

According to another embodiment of the present invention, the frequency of the ultrasonic wave in the removal method is preferably 18 to 1000kHz range.

According to another embodiment of the present invention, it is preferable that the pressure at the time of decompression in the removal method is 20 to 759 Torr.

According to another embodiment of the present invention, the polymer in the removal method is polyvinyl chloride, polyvinylidene chloride, polyvinylacetate, polyvinyl alcohol polystyrene, polymethyl methacrylate, vinyl chloride vinyl acetate copolymer and acrylonitrile It is preferably at least one polymer selected from the group consisting of butadiene styrene copolymers and the like.

According to another embodiment of the invention, the temperature of the polymer in the removal method is preferably 30 to 100 ℃.

According to another embodiment of the present invention, in the removal method

Introducing a polymer comprising unreacted monomers into a degassing tank; And,

Irradiating the polymer under reduced pressure in a degassing tank to remove unreacted monomers and volatiles other than unreacted monomers from the polymer;

It is preferable to include.

According to another embodiment of the invention, it is preferable to stir the polymer using a stirring means in the reactor while irradiating the ultrasonic wave in the step of irradiating the ultrasonic wave in the removal method.

According to another embodiment of the invention, the stirring speed of the stirring means in the removal method is preferably 5 to 1200 rpm. According to another embodiment of the present invention, in the manufacturing method

Injecting a vinyl chloride polymer slurry or latex comprising unreacted vinyl chloride monomer into a degassing tank; And,

Irradiating an ultrasonic wave of 18 to 1000 kHz while stirring the polymer slurry under a pressure of 20 to 759 Torr in a degassing tank to remove unreacted monomers and volatiles other than unreacted monomers from the polymer;

It is preferable to include.

The present invention to achieve the second technical problem,

A degassing tank (1) for receiving a debris (6) containing an unreacted monomer;

A stirring device (3) connected to the stirring means existing inside the degassing tank (1);

An ultrasonic oscillator 4 mounted on one surface of the degassing tank 1;

A heating jacket 5 mounted on one surface of the degassing tank 1;

Transfer pump (7) is installed on the pipe connected to the upper portion of the degassing tank (1) to transfer the degassing material (6)

A drain pump (10) installed on a pipe connected to a lower portion of the degassing tank (1) to discharge the deaerator 6; And,

A vacuum pump (12) installed on a pipe connected to an upper space of the degassing tank (1) to depressurize the inside of the degassing tank (1) in a vacuum state;

It provides an unreacted monomer removal device consisting of.

Unlike the conventional method of applying ultrasonic waves while using a carrier gas, the method for removing unreacted monomers of the present invention removes and recovers unreacted monomers from latex or slurry with excellent efficiency without using carrier gas by applying ultrasonic waves under vacuum. Maintain quality, reduce environmental pollution and reduce costs.

Hereinafter, the present invention will be described in more detail.

The present invention provides a method for removing unreacted monomers by irradiating a polymer containing unreacted monomers under reduced pressure to remove unreacted monomers and volatiles other than unreacted monomers from the polymer.

When ultrasonic waves are oscillated through an ultrasonic oscillator composed of a piezoelectric element, ultrasonic waves propagate through a solution. At this time, a cavitation phenomenon occurs and a minute low pressure cavity is generated. The cavities are created and dissipated in a very short time, and the number, size, and momentum of the cavities vary according to the oscillated ultrasonic frequency, temperature and pressure of the solution. As the cavity develops and disappears, it is accompanied by a sharp change in pressure, and the residual unreacted monomer is separated from the polymer by a cavity that forms and dissipates near the effluent. In order to more easily separate the vaporized volatile unreacted monomer, it is possible to increase the separation efficiency by using an inert gas such as nitrogen as the carrier gas. However, in the present invention, by lowering the pressure by applying a vacuum, as a result, the boiling point of the volatile unreacted monomers is lowered, so that the volatile unreacted monomers can be more easily separated without a separate carrier gas. In this case, it is possible to maintain the physical properties of the polymer in that there is no excessive temperature rise.

In particular, the monomer removal method of the present invention is easy to recover after the residual monomer gas is separated from the stripping material. That is, re-entry into the process is easy. In the conventional method, since the carrier gas) and the monomer are mixed and discharged, it is difficult to separate them again and high cost is required. For example, in the case of degassing using steam, which is a technique mainly used for separating unreacted monomers, the degassing using steam is also a technique used in actual processes because it is easy to separate unreacted monomers and steam through compression and cooling of steam after degassing.

Therefore, it is very important in terms of process and economics that the monomer can be easily recovered without a separate process. For example, in the case of PVC (polyvinyl chloride) used in the embodiment of the present invention, since the cost of the monomer, VCM (vinyl chloride monomer) accounts for about 60 to 70% of the total production cost, Especially important.

In addition, when degassing the monomer from the polymer in the latex state, the use of a carrier gas causes difficulties in actual degassing operation due to bubble generation, etc., but there is no problem as described above in the case of using a carrier gas as in the present invention. There is an advantage.

The polymer used in the present invention is preferably in one state selected from the group consisting of slurry or latex, but is not limited thereto and includes all types of polymers produced in the art.

The frequency of the ultrasonic waves used in the present invention is preferably in the range of 18 to 1000 kHz. If the frequency is below 18 kHz or above 1000 kHz, the degassing effect is negligible.

In the present invention, the pressure at the time of reduced pressure applied together with the ultrasonic wave is preferably 20 to 759 torr. If the pressure is less than 20torr, there is a problem that the solvent used in the latex or slurry polymer is volatilized together and there is a problem of economical efficiency. If the pressure exceeds 759torr, there is almost no difference in volatility due to reduced pressure.

In the present invention, the polymer may be used for all kinds of polymers containing unreacted monomers used in the art. The polymer does not necessarily need to be a homopolymer and a copolymer comprising two or more monomers is also possible.

In the present invention, the polymer used in the removal method is preferably maintained at a temperature of 30 to 100 ℃ in terms of degassing efficiency using ultrasonic waves, and should be maintained within a temperature range for maintaining the quality of the polymer. For example, in the case of polyvinyl chloride, it is preferable to keep it at 100 degrees C or less for a slurry, and to 65 degrees C or less for a latex. If the temperature exceeds 100 ℃ there is a problem that the ultrasonic degassing effect is reduced and the product quality deteriorates.

More specifically, the removal method of the present invention comprises the steps of injecting a polymer containing an unreacted monomer into the reactor; And ultrasonically irradiating the polymer under reduced pressure in the reactor to remove unreacted monomers and volatiles other than unreacted monomers from the polymer. For example, a polymer in the form of latex or slurry containing unreacted monomer is introduced into a reactor, the reactor is sealed, and the pressure inside the reactor is reduced, followed by ultrasonic irradiation of the polymer to remove unreacted monomer and other volatile substances. Remove from polymer slurry or latex.

In the present invention, it is preferable to stir the polymer using a stirring means in the reactor while irradiating the ultrasonic waves in the step of irradiating the ultrasonic waves. By stirring the polymer evenly by this stirring, it is possible to promote the separation of volatiles and to obtain a polymer of uniform quality. It is preferable that the stirring speed of the said stirring means is 5-1200 rpm. If the stirring speed is less than 5rpm, there is a problem in mixing the solution of the polymer, there is a problem that the degassed unreacted monomer does not easily escape to the gas phase. In the case of 1200 rpm or more, the increase in the degassing effect due to the increase in the stirring speed is minimal.

As a specific embodiment of the present invention, the step of introducing a vinyl chloride polymer slurry or latex containing an unreacted vinyl chromide monomer into the reactor; And irradiating ultrasonic waves at 20 to 100 kHz while stirring the polymer at 100 to 500 rpm under a pressure of 50 to 250 torr in the reactor to remove unreacted monomers and volatiles other than unreacted monomers from the polymer. Do.

The present invention to achieve the second technical problem,

On a surface of the degassing tank 1, a degassing tank 1 containing unreacted monomers 6, a stirring device 3 connected to a stirring means existing inside the degassing tank 1, Ultrasonic oscillator 4 mounted, a heating jacket 5 mounted on one surface of the degassing tank 1, a conveyance installed on a pipe connected to the upper part of the degassing tank 1 to transport the debris 6 The pump 7 is installed on the pipe connected to the lower part of the degassing tank 1 and installed on the drain pump 10 for discharging the debris 6 and the pipe connected to the upper space of the degassing tank 1. The present invention provides an unreacted monomer removal apparatus composed of a vacuum pump 12 for depressurizing the inside of the degassing vessel 1 in a vacuum state. The removal device is shown in FIG.

In more detail with respect to the removal device, the degassing tank 1 is degassed slurry or latex to be degassed. The degassing tank 1 is attached with a stirring device 3 to which an upper lid 2 and a stirring means (for example, an impeller) are connected. Stirring at an appropriate rotational speed through the stirring device 3 prevents precipitation of the slurry and evenly disperses the slurry in the degassing tank to promote degassing action. The ultrasonic wave oscillator 4 is used to generate ultrasonic waves, and the heating jacket 5 is used to keep the slurry or the like at a temperature suitable for degassing. Inside the degassing tank 1, a degassing substance 6 containing an unreacted monomer is introduced. Such mortars are, for example, polymers in the form of slurries or latex. The transfer pump 7 transfers the polymer latex or slurry produced after the polymerization reaction to a degassing tank at a constant speed, and is input to the degassing tank through the input unit 8. The drain valve 9 and the drain pump 10 serve to send a slurry or latex from which residual monomers are removed after degassing for a predetermined time to a dehydration or drying process, which is a post process. The degassed unreacted monomer and other volatiles are discharged through the degassing outlet 11 and a vacuum pump 12 is attached to keep the inside of the degassing tank under reduced pressure to facilitate the degassing. It is possible to effectively remove unreacted monomers and the like from the polymer in latex or slurry form using the removal device.

Hereinafter, the present invention will be described in more detail, but the following examples are provided for the purpose of explanation and are not intended to limit the present invention.

Example 1

1200g (solid content: 50 wt%) of PVC latex (LG Chem. Polymerization degree 1000) was added to a 5L degassing tank, and the temperature inside the degassing tank was raised to 55 ° C, and the pressure inside the degassing tank was reduced to 250torr. While maintaining and stirring the latex at 80 rpm using an agitator, ultrasonic waves at a frequency of 40 kHz were irradiated to degas unreacted monomers.

Example 2

The same procedure as in Example 1 was conducted except that the rotation speed of the stirring device was 120 rpm and the ultrasonic frequency was 20 kHz.

Example 3

The same procedure as in Example 1 was carried out except that the rotation speed of the stirring device was 120 rpm and the ultrasonic frequency was 40 kHz.

Example 4

The same procedure as in Example 1 was carried out except that PVC slurry (LG Chem. Polymerization degree 1000) was used instead of PVC latex.

Comparative Example 1

The same process as in Example 1 was conducted except that the temperature of the latex was maintained at 60 ° C. without applying vacuum and ultrasonic waves.

Comparative Example 2

The same process as in Example 1 was carried out except that the stirring speed was 120 rpm and the ultrasonic frequency was 40 kHz while supplying nitrogen at a rate of 250 ml / min as a carrier gas without applying a vacuum.

Comparative Example 3

The same procedure as in Comparative Example 1 was conducted except that the PVC slurry was used instead of the PVC latex.

Determination of residual unreacted monomer content in latex or slurry

While performing the degassing experiment according to Examples 1 to 4 and Comparative Examples 1 to 3, 2g of the latex or slurry samples were collected over time and put into a vial, and then measured by gas chromatography (G / C) analysis. It was. The analytical instrument was Agilent 7694 Headspace Sampler (G1883) and Agilent 6890 GC / FID and heated to 90 ° C. for 20 minutes. The experimental results are shown in Table 1 below. In the case of the data value is different from the initial value according to the sample is difficult to compare with each other it is shown in Figure 2 converted to a relative value.

In FIG. 2, RVCM (%) is defined as Equation 1 as relative vinyl chloride monomer (VCM) content.

<Equation 1>

RVCM (%) = RVCM _{(t = t1)} / RVCM _{(t = 0)}

RVCM _{(t = t1 )} is the content of unreacted VCM in latex or slurry at time t ₁ (ppm)

RVCM _{(t = 0)} is the content of unreacted VCM in latex or slurry prior to degassing (ppm)

Evaluation of stability of latex

After removing the unreacted monomer, it was confirmed whether coagulation of latex particles occurred.

No aggregation phenomenon: Excellent stability

Aggregation phenomenon: Poor stability

Minutes stability 0 10 20 30 60 90 evaluation Example 1 1749.5 - 942.8 - 422.8 260.2 Great Example 2 1448.9 972.7 - 571.1 275.1 146.5 Great Example 3 1399.0 683.6 486.9 331.3 167.8 81.6 Great Example 4 9624.5 - - 5519.4 1364.4 - Comparative Example 1 1381.9 1288.6 - 1236.5 1230.5 Great Comparative Example 2 1902.9 1240.9 1047.3 810.7 474.1 Bad Comparative Example 3 9600 9135.1 - 8685.1 8439.3 -

As shown in Table 1 and Figure 2, in Examples 1 to 4 using the method of the present invention after 60 minutes the VCM content present in the polymer latex or slurry was reduced to less than 30% of the initial value. In contrast, in the case of Comparative Example 2 using ultrasonic and carrier gas, the content of VCM decreased to about 25% after 60 minutes, but the stability of latex was decreased by using carrier gas. Has occurred excessively, resulting in difficulty in operation. In Comparative Examples 1 and 3 in which no ultrasonic wave, vacuum, and carrier gas were used at all, it was found that even after 60 minutes, the RVCM (%) was maintained almost at 90% level. This difference in stability of RVCM (%) and latex is due to the effective degassing of the remaining unreacted monomer from the scavengers without the use of a carrier gas by irradiating the scavengers with ultrasonic waves under vacuum. Therefore, it is determined that the above method can be used to remove and recover unreacted monomers more efficiently in the actual process.

The method of removing unreacted monomers of the present invention enables the in-process recycling of degassed unreacted monomers by degassing and recovering unreacted monomers from latex or slurry with excellent efficiency without the use of a carrier gas by irradiating ultrasonic waves to the skin to be removed under vacuum. Therefore, it has the effect of reducing the operating cost, maintaining the excellent quality of the product and reducing the environmental pollution.

Claims (11)

A method of removing unreacted monomers by irradiating a polymer containing unreacted monomers under reduced pressure to remove unreacted monomers and volatile substances other than unreacted monomers from the polymer. The method of claim 1, wherein the polymer is in the form of a slurry or latex capable of ultrasonic propagation. The method of claim 1, wherein the frequency of the ultrasonic wave is in the range of 18 to 1000kHz. The method of claim 1, wherein the pressure at reduced pressure is 20 to 759 Torr. The method of claim 1, wherein the polymer is polyvinyl chloride, polyvinylidene chloride, polyvinylacetate, polyvinyl alcohol polystyrene, polymethyl methacrylate, vinyl chloride vinyl acetate copolymer, acrylonitrile butadiene styrene copolymer, or the like. Unreacted monomer removal method, characterized in that at least one polymer selected from the group consisting of. The method of claim 1, wherein the temperature of the polymer is 30 to 100 ℃ unreacted monomer removal method. The method of claim 1, Introducing a polymer comprising unreacted monomers into a degassing tank; And, Irradiating the polymer under reduced pressure in a degassing tank to remove unreacted monomers and volatiles other than unreacted monomers from the polymer; Unreacted monomer removal method comprising a. The unreacted monomer removing method according to claim 7, wherein the polymer is agitated using a stirring means in a degassing tank while irradiating the ultrasonic waves in the irradiating the ultrasonic waves. 9. The method for removing unreacted monomers according to claim 8, wherein the stirring speed of the stirring means is 5 to 1200 rpm. The method of claim 1, Injecting a vinyl chloride polymer comprising an unreacted vinyl chloride monomer into a degassing tank; And, Irradiating ultrasonic waves at 20 to 100 kHz with stirring the polymer under a 50 to 250 torr pressure in a degassing tank to remove unreacted monomers and volatiles other than unreacted monomers from the polymer; Unreacted monomer removal method comprising a. A degassing tank (1) for receiving a debris (6) containing an unreacted monomer; A stirring device (3) connected to the stirring means existing inside the degassing tank (1); An ultrasonic oscillator 4 mounted on one surface of the degassing tank 1; A heating jacket 5 mounted on one surface of the degassing tank 1; Transfer pump (7) is installed on the pipe connected to the upper portion of the degassing tank (1) to transfer the degassing material (6) A drain pump (10) installed on a pipe connected to a lower portion of the degassing tank (1) to discharge the deaerator 6; And, A vacuum pump (12) installed on a pipe connected to an upper space of the degassing tank (1) to depressurize the inside of the degassing tank (1) in a vacuum state; Unreacted monomer removal device consisting of.

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