JP2007169305A - Method for recovering rubber from organic waste liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for effectively separating and recovering rubber from an organic waste liquid containing the rubber so as to improve the recovery rate of the organic solvent. <P>SOLUTION: This method for recovering the rubber from the organic waste liquid containing the rubber and the organic solvent dissolving the rubber comprises a process of adding liquefied carbon dioxide to the organic waste liquid under a pressurized state so as to deposit the rubber in a mixed liquid of the organic waste liquid and liquefied carbon dioxide, and a process of solid liquid-separating the mixed liquid under the pressurized state so as to recover the rubber deposited in the mixed liquid. The method preferably further includes a process of vaporizing the liquefied carbon dioxide by heating or pressure-reducing the mixed liquid from which the deposited rubber is recovered, under the same pressure and recovering the organic solvent and carbon dioxide, and also it is preferable to perform the liquid solid separation of the mixed liquid under pressurized state by using a liquid cyclone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of separating and recovering rubber from organic waste liquid containing rubber discharged mainly in rubber production and rubber product processing.

A large amount of organic waste liquid containing rubber and an organic solvent in which the rubber is dissolved is inevitably generated in a rubber manufacturing factory or a rubber product processing factory. The treatment of waste liquid discharged from factories in recent years and environmental problems are important social problems. These organic waste liquids containing rubber discharged from factories are not only incinerated, but also the raw materials such as rubber and rubber are dissolved. It is important to collect and reuse organic solvents such as benzene and toluene. Conventionally, as a method for recovering rubber from organic waste liquid containing rubber, the organic waste liquid containing rubber stored in a container is vacuum-dried or heat-distilled in a state of being stored in the container to volatilize the solvent from the organic waste liquid. A method for recovering rubber has been proposed (see, for example, Patent Document 1).
JP 2001-226410 A (specification [0021])

However, when the organic waste liquid containing rubber is vacuum-dried or heated and distilled to volatilize the solvent, the rubber concentration in the waste liquid increases and the viscosity in the organic waste liquid increases rapidly. And the rubber density | concentration in the gas-liquid contact surface in the organic waste liquid in which a solvent actually volatilizes increases remarkably, and when the volatilization of a solvent advances, a rubber film with high viscosity will be formed on the surface in the organic waste liquid stored in the container. When a rubber film is formed on the surface of the organic waste liquid, the solvent in the organic waste liquid existing below the rubber film cannot be effectively volatilized, and as a result, the rubber is effectively recovered in a solid state. There was a bug that could not be done. Moreover, since the vapor phase concentration of the organic solvent removed by volatilization is low, there is another problem that the effect of recovering the organic solvent from the volatilized gas is low.
The objective of this invention is providing the collection | recovery method of the rubber | gum from the organic waste liquid which can isolate | separate and collect rubber | gum effectively from the organic waste liquid containing a rubber | gum.
Another object of the present invention is to provide a method for recovering rubber from an organic waste liquid that can improve the recovery rate of the organic solvent from the organic waste liquid containing rubber.

As shown in FIG. 1, the invention according to claim 1 is an improvement of a method for recovering rubber and organic solvent from an organic waste liquid containing rubber and an organic solvent in which the rubber is dissolved.
The characteristic point is that liquid carbon dioxide is added to the organic waste liquid under pressure to deposit rubber in the mixed liquid consisting of organic waste liquid and liquid carbon dioxide, and the mixed liquid is solid-liquid separated under pressure. And collecting the rubber precipitated in the mixed liquid.
In the method for recovering rubber from the organic waste liquid described in claim 1, since the rubber is recovered by solid-liquid separation after the rubber is once deposited, a rubber film that prevents volatilization of the organic solvent is formed. The rubber can be effectively separated and recovered from the organic waste liquid containing the rubber.

The invention according to claim 2 is the invention according to claim 1, wherein the mixed liquid after the deposited rubber is recovered is heated or depressurized to vaporize liquid carbon dioxide to recover the organic solvent and carbon dioxide. The method further includes a step.
The mixed liquid after the rubber is removed includes an organic solvent in which the rubber is dissolved and liquid carbon dioxide added thereafter. In the method for recovering rubber from the organic waste liquid described in claim 2, the mixed liquid after the rubber has been removed can be recovered by separating the organic solvent and the liquid carbon dioxide, and the organic solvent is volatilized. Compared with this method, the recovery rate of the organic solvent from the organic waste liquid containing rubber can be improved.
The invention according to claim 3 is the invention according to claim 1 or 2, characterized in that solid-liquid separation of the mixed liquid in a pressurized state is performed by the liquid cyclone 16.
In the method for recovering rubber from the organic waste liquid according to the third aspect, the rubber can be effectively separated and recovered from the mixed liquid in which the rubber is deposited.

  In the method for recovering rubber from the organic waste liquid according to the present invention, a step of adding liquid carbon dioxide to the organic waste liquid to precipitate the rubber in the mixed liquid composed of the organic waste liquid and the liquid carbon dioxide; And a process of collecting the rubber separated in the liquid mixture and separating the rubber from the organic waste liquid containing rubber without forming a rubber film that prevents the volatilization of the organic solvent. It can be recovered. The mixed liquid after the rubber is removed includes an organic solvent in which the rubber is dissolved and liquid carbon dioxide added thereafter. Therefore, the mixed liquid after the rubber has been removed is further obtained by heating or depressurizing the mixed liquid after the precipitated rubber is recovered to vaporize the liquid carbon dioxide to recover the organic solvent and carbon dioxide. The organic solvent and carbon dioxide can be separated and recovered from the organic solvent, and the recovery rate of the organic solvent from the organic waste liquid containing rubber can be improved. In this case, if the solid-liquid separation of the mixed liquid under pressure is performed by a liquid cyclone, the rubber can be effectively separated and recovered from the mixed liquid on which the rubber is deposited.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
As shown in FIG. 1, the present invention is a method for recovering rubber from an organic waste liquid, and the target organic waste liquid contains rubber and an organic solvent in which the rubber is dissolved. Here, examples of the rubber include natural rubber (NR) and synthetic rubber. Synthetic rubbers include isoprene rubber (IR), styrene butadiene rubber (SBR), butyl rubber (IIR), butadiene rubber (BR), ethylene propylene rubber (EPDM), nitrile rubber (NBR), chloroprene rubber (CR), hypalon ( CSM), urethane rubber (U), polysulfide rubber (T), silicone rubber (Q), fluoro rubber (FKM), acrylic rubber (ACM), epichlorohydrin rubber (ECO), and the like. Moreover, as an organic solvent, benzene, toluene, xylene, trichlene, ether etc. which can melt | dissolve these rubber | gum are mentioned.

  In the method for recovering rubber from the organic waste liquid in the present invention, the step of adding liquid carbon dioxide to the pressurized organic waste liquid and precipitating the rubber in a mixed liquid composed of the organic waste liquid and liquid carbon dioxide, and mixing Separating the liquid into a solid-liquid separation in a pressurized state and separating the recovered solid rubber from the mixed liquid and recovering it, and heating the remaining mixed liquid after recovering the rubber or A step of evaporating liquid carbon dioxide to recover the organic solvent and carbon dioxide. These are described below.

<Rubber precipitation process>
First, as shown in FIG. 1 (a), liquid carbon dioxide is added to the organic waste liquid to lower the solubility of the rubber. As shown in FIG. 1 (b), the rubber is mixed into the mixed liquid composed of the organic waste liquid and liquid carbon dioxide. To precipitate. Here, carbon dioxide becomes liquid by being pressurized using a pump (not shown). In the present invention, since liquid carbon dioxide is added to the organic waste liquid, if the mixed liquid composed of the organic waste liquid containing rubber and the liquid carbon dioxide is 10 to 30 ° C., the pressure is preferably increased to 4.0 to 8.0 MPa.

  The amount of liquid carbon dioxide added to the organic waste liquid is preferably 100 to 10,000 wt% when the organic waste liquid containing rubber is 100 wt%. If the amount of liquid carbon dioxide added is less than 100% by weight, it will be difficult to sufficiently precipitate the rubber. If the amount of liquid carbon dioxide added exceeds 10,000% by weight, the liquid carbon dioxide will be recovered in a subsequent step. There is a problem that increases the burden of A more preferable range of the addition amount of the liquid carbon dioxide is 500 to 5000% by weight when the organic waste liquid containing rubber is 100% by weight.

  As shown in FIG. 2, in order to continuously treat the organic waste liquid, it is preferable to add liquid carbon dioxide to the organic waste liquid and stir using the line mixer 11. In the apparatus shown in FIG. 2, the organic waste liquid is supplied with pressure by the high-pressure pump 12 and supplied to the line mixer 11 in a pressurized state. On the other hand, liquid carbon dioxide is stored in the fluid storage cylinder 13 and supplied to the line mixer 11 in a state where the liquid state is maintained by the circulation pump 14. The line mixer 11 is provided with a plurality of baffle plates therein, and is configured so that the organic waste liquid and liquid carbon dioxide supplied to one end pass through the plurality of baffle plates when going to the other end that has passed through the inside. By passing through the plurality of baffle plates, both are sufficiently mixed to obtain a mixed liquid composed of organic waste liquid and liquid carbon dioxide. Then, the organic waste liquid and the liquid carbon dioxide are sufficiently agitated and mixed by the line mixer 11 configured in this manner, so that the solubility of the rubber is lowered and the rubber is continuously obtained in the obtained mixed liquid. It can be deposited.

<Solid-liquid separation process>
In this step, as shown in FIG. 1B, the mixed liquid in which the rubber is deposited is solid-liquid separated as shown in FIG. 1C while maintaining the pressurized state. And the rubber | gum which precipitated and became solid and was isolate | separated from the liquid is collect | recovered. In this solid-liquid separation, as shown in FIG. 1 (c), the mixed liquid in which the rubber is precipitated may be left still in a pressurized state, and the precipitated rubber may be allowed to settle, which is shown in FIG. Such a liquid cyclone 16 may be used. The hydrocyclone 12 shown in FIG. 2 has a funnel-shaped container body 16a having a gentle inclination, a lid body 16b for sealing the upper part of the container body 16a, and a ball valve 16c for sealing the lower part of the container body 16a. The lid body 16b is provided with an inlet 16d for supplying the pressurized mixed liquid in which the rubber is deposited to the inside of the container body 16a and an outlet 16e for discharging the mixed liquid from which the rubber has been removed to the outside. Then, the mixed liquid in a pressurized state in which the rubber is deposited is poured along the edge of the container body 16a from the upper part of the container body 16a through the inlet 16d so as to vortex inside the container body 16a. When the mixed liquid rotates so as to vortex inside the container body 16a, the precipitated and solid rubber is separated from the liquid by centrifugal force and reaches the ball valve 16c.

On the other hand, in the liquid cyclone 16, the mixed liquid, which is a liquid, rises from the center of the container body 16a and is discharged from an outlet 16e formed in the lid body 16b with the rubber removed. In this way, the mixed liquid is solid-liquid separated in a pressurized state, and by opening the ball valve 16c, the rubber deposited in the mixed liquid can be discharged from the container body 16a and collected. When such a liquid cyclone 16 is used, the organic waste liquid can be continuously processed by continuously providing the liquid cyclone 16 in the line mixer 11 in the previous stage. In the apparatus shown in FIG. 2, the rubber storage tank 17 is provided below the ball valve 16c, and the rubber discharged by opening the ball valve 16c is configured to be stored at normal temperature and normal pressure.
As described above, in the method for recovering rubber according to the present invention, since the rubber is once precipitated and then solid-liquid separated, the rubber can be effectively separated and recovered from the organic waste liquid containing rubber.

<Heating and decompression process>
As shown in FIG. 1D, the mixed liquid after the rubber has been removed contains an organic solvent in which the rubber is dissolved and liquid carbon dioxide added thereafter. This step is performed in order to reuse them, and separates and recovers the organic solvent and liquid carbon dioxide from the mixed liquid after the rubber is removed. The separation of the organic solvent and the liquid carbon dioxide is preferably performed by vaporizing the liquid carbon dioxide. The vaporization of the liquid carbon dioxide is performed by heating or depressurizing the mixed liquid in the same pressure state after collecting the deposited rubber. It is preferable to do so.

  A gas-liquid storage tank 19 is connected to an outlet 16e of the liquid cyclone 16 shown in FIG. 2 via a heater 18, and the mixed liquid discharged from the outlet 16e is separated from the solid rubber by the liquid cyclone 16. It is comprised so that it may be heated by and may be stored in the gas-liquid storage tank 19 after that. When the mixed liquid of, for example, 20 ° C. is heated to, for example, 40 ° C. by the heater 21 when discharged from the liquid cyclone 16, about 60% of the liquid carbon dioxide is vaporized. Further, a solvent recovery tank 22 is connected to the lower part of the gas-liquid storage tank 19 via a pressure valve 21, and the upper part of the gas-liquid storage tank 19 is connected to the fluid storage cylinder 13 via a cooler 23. The carbon dioxide in the gas-liquid storage tank 19 transformed from a liquid to a gas reaches the cooler 23 from the upper part of the gas-liquid storage tank 19, is cooled by the cooler 23, is liquefied again, and is stored in the fluid storage cylinder 13. Reused.

  On the other hand, about 40% of the liquid carbon dioxide initially added to the organic waste liquid still remains as a liquid in the mixed liquid stored in the gas-liquid storage tank 19. When the pressure valve 21 is opened, the mixed liquid stored in the gas-liquid storage tank 19 is depressurized and reaches the solution recovery tank 22. When the liquid stored in the gas-liquid storage tank 19 is depressurized, most of the carbon dioxide present in the liquid is vaporized, and the liquid depressurized to atmospheric pressure and stored in the solution recovery tank 22 is an organic waste liquid. It becomes an organic solvent in which rubber is dissolved. By doing in this way, the recovery method of the rubber | gum of this invention can improve the recovery rate of the organic solvent from the organic waste liquid containing rubber | gum compared with the conventional method of volatilizing an organic solvent.

  Then, if the upper part of the solution recovery tank 22 is connected to the fluid storage cylinder 13 via the compressor 24 as shown by a broken line in FIG. 2, carbon dioxide transformed from a liquid to a gas is extracted from the upper part of the solution recovery tank 22. Then, the liquid carbon dioxide can be reused by being liquefied again by the compressor 24 and then stored in the fluid storage cylinder 13. If carbon dioxide is recovered and stored in the fluid storage cylinder 13 as described above, the liquid carbon dioxide added to the organic waste liquid can be recovered and reused without being diffused outside.

Next, an example performed to confirm the effect of the present invention will be described with reference to FIG.
<Example 1>
As an organic waste liquid, 40 kg of rubber (NBR) and 60 kg of toluene as an organic solvent were prepared, and both were put into the mixing stirrer 16 shown in FIG. 1 and mixed and stirred. The rubber (NBR) was 40 wt%, and the organic solvent An organic waste liquid containing 60% by weight of (toluene) was obtained.
Next, this organic waste liquid was supplied with pressure to the line mixer 11 while being pressurized to 6 MPa by applying a pressure with a high-pressure pump 12 at 20 ° C. In parallel with this, liquid carbon dioxide stored in the fluid storage cylinder 13 was supplied to the line mixer 11 while being pressurized to 6 MPa by the circulation pump 14. The supply amount of the liquid carbon dioxide was set to be 10 times the supply amount of the organic waste liquid, and both were sufficiently mixed to obtain a mixed liquid composed of the organic waste liquid and the liquid carbon dioxide. And the solubility of rubber | gum was reduced and the rubber | gum was deposited in the mixed liquid. The supply amount of liquid carbon dioxide corresponds to 1000% by weight when the organic waste liquid is 100% by weight.

Next, the mixed liquid composed of the organic waste liquid and liquid carbon dioxide is put into the liquid cyclone 16 while maintaining a state of 6 MPa at 20 ° C., and the precipitated and solid rubber is separated from the liquid. The rubber separated by opening was discharged from the container body 16a and collected.
The mixed liquid from which the deposited rubber was separated and discharged from the outlet 16e of the liquid cyclone 16 was heated to 40 ° C. by the heater 21 while maintaining a pressure of 6 MPa, and stored in the gas-liquid storage tank 19. Next, the pressure valve 21 is opened, and the liquid stored in the gas-liquid storage tank 19 is moved to the solution recovery tank 22 while being decompressed and stored, and toluene, which is an organic solvent in which rubber in the organic waste liquid is dissolved, is recovered. It was stored in the tank 22.
And when the weight of the rubber | gum which is the solid isolate | separated from the liquid with the liquid cyclone 16 was measured, it was 39.9 kg. For this reason, it was found that the rubber was quantitatively recovered because the weight of the rubber thus obtained was 99% or more of the rubber initially mixed with toluene to obtain the organic waste liquid. . Further, the weight of toluene stored in the solution recovery tank 22 was measured and found to be 58.5 kg. Since this is 97.5% of the amount originally used to obtain the organic waste liquid, in the present invention, the recovery rate of the organic solvent from the organic waste liquid containing rubber is improved as compared with the conventional one. I knew I would get it.

It is a figure showing each process of a recovery method of rubber of an embodiment of the present invention. It is a figure which shows the structure of the apparatus used for the collection | recovery method of the rubber | gum.

Explanation of symbols

16 Hydrocyclone

Claims (3)

In a method of recovering the rubber and the organic solvent from an organic waste liquid containing rubber and an organic solvent in which the rubber is dissolved,
Adding liquid carbon dioxide to the pressurized organic waste liquid to deposit the rubber in a mixed liquid composed of the organic waste liquid and the liquid carbon dioxide;
Recovering the rubber from the organic waste liquid, comprising: solid-liquid separation of the mixed liquid under pressure and recovering the rubber deposited in the mixed liquid.   The method for recovering rubber from an organic waste liquid according to claim 1, further comprising a step of heating or depressurizing the mixed liquid after the precipitated rubber is recovered to vaporize liquid carbon dioxide to recover the organic solvent and carbon dioxide. The method for recovering rubber from an organic waste liquid according to claim 1 or 2, wherein the solid-liquid separation of the mixed liquid under pressure is performed by a liquid cyclone (16).

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