JPS6328411A - Method for recovering solvent - Google Patents

Abstract

PURPOSE:To efficiently and precisely separate a solvent and free water and to recover the solvent alone by incorporating a filter consisting of a specific fibrous structure into a sp.gr.-difference separation stage to selectively passing the solvent alone through the filter. CONSTITUTION:A filter consisting of a water-repellent fibrous structure of polytetrafluoroethylene fiber, polypropylene fiber, etc., consisting essentially of a filament of 0.1-10mum diameter and having 30-90% porosity is incorporated in a separation stage wherein solvent and free water are stationarily separated by the difference in sp.gr. in a separator of specific size, and a solvent such as n-pentane and n-hexane is selectively passed through the filter. For example, a water-solvent mixture 21 flowing into the separator 19 from an inlet 18 is separated into solvent and water by the sheet filter 20 using this method. Namely, the solvent alone is passed through the filter 20, the separated solvent is introduced to a solvent recovery outlet 23, and the water is discharged from a water outlet 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of separating water droplets finely dispersed as free water in a solvent and recovering only the solvent with high precision.

[Prior art]

Technology for separating solvent and water is in high demand in fields such as solvent recovery and reuse. For example, separation of moisture in cleaning solvents in precision cleaning machines for machinery, electronic parts, etc., Drike+7
, separation of water in a cleaning solvent in a cleaning machine, and separation of water in a solvent in a solvent recovery device using activated carbon or activated carbon fiber.

As a technology for separating water in these solvents, the specific gravity separation method, which utilizes the difference in specific gravity between the solvent and water, is generally adopted in many fields as one of the separation methods that can separate water in a single step and at low cost. There is.

For example, in the case of a dry cleaning machine, the solvent and water are separated as shown in FIG. 1, and the solvent is recovered and reused. That is, the laundry items are transferred together with the solvent from the wash tank 6 to the rotating drum 1 for washing, and all or part of the dirty solvent is put into the distiller 2 for distillation.

Textile products subjected to dry cleaning may undergo dimensional changes due to shrinkage, wrinkles, or
Since deterioration of shape, color, gloss, texture, etc. occurs, the recovered solvent coming out from the distiller 2 through the cooler 3 is separated by specific gravity difference in order to prevent free water from being mixed into the recovered solvent. Vessel 4
The solvent and water are separated and only the solvent is collected in a clean tank 5 for reuse.

As another example 11, in the case of a precision cleaning machine using ultrasonic waves, the solvent and water are separated as shown in FIG. 2, and the solvent is recovered and reused. That is, the ultrasonic oscillator 8t
- Treat the object to be cleaned in the ultrasonic cleaning tank 7 provided, and
The solvent vaporized in the ultrasonic cleaning tank 7 and the steam tank 8 is condensed into a liquid in the cooling pipe 10. At this time, moisture in the atmosphere is also condensed at the same time, so the moisture is mixed and dispersed in the solvent. In order to separate this moisture, only the solvent is recovered and reused through the specific gravity difference separator 11.

As another example, in the case of a solvent recovery device using granular activated carbon or activated carbon fiber, the solvent and water are separated as shown in FIG. 3, and the solvent is recovered and reused. That is, the raw gas containing the solvent gas is transferred to the activated carbon adsorption tank 1 from 12.
3, and the solvent gas is adsorbed onto the activated carbon. The adsorbed gas is desorbed from the activated carbon by water vapor blown in from 14, and condensed into liquid by cooling RF 15.
At this time, water is mixed into the solvent, but a specific gravity difference separator 16 is installed for the purpose of separating this water, and only the solvent is recovered and reused.

[Problem that the invention seeks to solve]

In any of the above-mentioned dry cleaning machines, precision cleaning machines, and layer agent recovery equipment, the free water droplets in the solvent that come out through the cooler are minute water droplets with a size of 10 μm or less. If such an amount exists, there is a problem that the solvent and water cannot be separated sufficiently by the residence time in the specific gravity difference separator alone. One possible way to improve the above problem is to increase the capacity of the specific gravity separator to lengthen the residence time, but this would be impractical because the equipment would be large, and it would be difficult to remove free water in the solvent efficiently and efficiently. Separate to precision,
A method of recovering only the solvent was strongly desired.

An object of the present invention is to improve the problems of the conventional techniques described above, and to provide a method for efficiently and highly accurately separating solvent and free water, and recovering only the solvent.

[Means for solving problems]

The present inventors discovered that a water-repellent fibrous structure made of ultrafine fibers has small pores and a high overall porosity, so it absorbs water finely dispersed in a solvent. The present invention was completed based on the knowledge that it is possible to reliably separate the solvent and allow only the solvent to permeate quickly.

That is, the method of the present invention for achieving the above-mentioned object is a method for separating a solvent and water by specific gravity separation.
The method is characterized in that the following filter (a) is incorporated into the specific gravity separation step to selectively allow the solvent to pass through.

(,) A filter consisting of a water-repellent fibrous structure mainly composed of fibers with a single fiber diameter of 0.1 to 10 pm and a porosity of 30 to 90 cm.

In the present invention, the "specific gravity separation process" refers to a specific gravity separation process in which a mixed solution of the solvent and free aqueous solution that comes out of the distillation and recovery process is processed in a specific gravity difference separator, as typified by dry cleaning machines and precision washing machines. The process of separating the solvent and water based on the difference in specific gravity between the solvent and water, and the process of separating the solvent and water in a specific gravity difference separator after desorbing and condensing the solvent adsorbed on activated carbon using steam, as in a solvent recovery device. etc. are representative, but are not limited to these. In short, any process may be sufficient as long as the process involves statically separating the solvent and free water in a specific gravity difference separator of a certain size using the difference in specific gravity between the solvent and water.

The "solvent" in the present invention has a surface tension of 55 dyne/
c! It is a liquid of n or less and has a different surface tension of 40 dyns/α.
The following liquids are preferable because they have good layer separation efficiency.

Typical examples of these solvents include various paraffinic hydrocarbons such as n-intane, n-hexane, n-hebutane, and n-decane, trichloroethylene, trichloroethane,
Tetrachloroethylene, tetrachloroethane, 1,1.
2-) Halogenated hydrocarbons such as 1.2゜2-trifluoroethane, mixtures of various hydrocarbon compounds such as petroleum ether, ligroin, gasoline, kerosene, and petroleum naphtha, aromatics such as benzene, toluene, and xylene Hydrocarbon compounds, alicyclic carbons represented by cyclopenkune and cyclohexane (including arsenic compounds, various mineral oils, vegetable oils, animal oils, various ethers, ketones, ester alcohols, phenols, etc.)

The "fibrous structure" used in the method of the present invention includes woven fabric, knitted fabric,
Although any type of nonwoven fabric may be used, a nonwoven fabric in which the size of each pore is small and a high overall porosity can easily be obtained is preferable because it has good water separation accuracy and a high permeation rate.

In the present invention, the "filter made of a water-repellent fibrous structure" means a water pressure resistance of 1001EIIH20 or more, preferably 2001EIIH20 or more, as measured by JIS-L-1092B method.
olH20 to 20001ImH20. The level of water resistance is usually 10 depending on the conditions of separation operation.
It may be appropriately selected within the range up to 000■H2o.

The fibers constituting the fiber structure of the present invention include polyester copolymers such as polyethylene terephthalate, polyethylene terephthalate azide, polyethylene terephthalate isophthalate, polyethylene terephthalate sepafoot, polyethylene terephthalate dodecanedioate, and polybutylene terephthalate. Fiber, polyheki length methylene adino! polyamide fibers, polyamides, imide fibers, aromatic polyamide fibers such as polyamide, polyhexamethylenedecamide, polyhexamethylenedecamide, polyhexamethylenehexamide, polycabramide, polyoctamide, polynonamide, polydecamide, Iridodecamide, and polytetramid. , fibers of polyester ethers such as linocra ethylene oxypenzoate, polyvinyl chloride, ? Halogen-containing composite fibers such as polyvinylidene chloride, polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyethylene, etc.? Examples include lyolefin fibers, various acrylic fibers, regenerated cellulose, acetate, cotton, linen, silk, and wool. These fibers may be used alone or in combination.

A specific example of a fiber structure having water repellency is as follows.

Examples include structures made of hydrophobic f1i fibers such as I-retetrafluoroethylene fibers, polypropylene fibers, and polyethylene fibers, and structures in which water repellency is imparted by applying a water repellent finish to a fiber structure. The water-repellent treatment of the fiber structure can be carried out using conventional methods, such as fluorocarbon resins such as acrylic acid, fluoroalcohol, silicone resins such as dimethyl silicone, paraffin resins, wax resins, etc. A water repellent agent is applied to the yarn manufacturing process or to the fiber structure by padding, dipping, spraying,
It may be added by a method such as exhaustion. Further, if necessary, heat treatment may be performed after applying a water repellent agent.

In the method of the present invention, it is necessary that the main fibers constituting the fibrous structure have a single fiber diameter of 0.1 μm to 10 μm. Single fiber diameter is t o tt
If it exceeds m, water droplets dispersed in the solvent (water droplets of 10 μm or less) will easily pass through the fiber structure, making it impossible to obtain sufficient separation accuracy, which is not preferable. Fibers smaller than 0.1 μm are difficult to produce uniformly industrially. Desirably, the main fibers have a diameter of 0.3 to 7 pm. "Mainly" means that the weight of fibers having the above-mentioned single fiber diameter is at least SOS, preferably at least 70% of the total weight of the fibers constituting the fibrous structure.

For example, if the fiber is uniform in diameter along its length,
Regarding fiber structures obtained by mixing fibers with various diameters, 0.1 of the single fibers in the fiber structure
It is sufficient if the weight of the fibers having a diameter of ˜10 μm is 50 inches or more.

The porosity of a water-repellent fibrous structure mainly composed of fibers with single fiber diameters of 0.1 μm and 10 μm must be in the range of 30 to 90 μm. Here, “porosity” is expressed by the following formula: defined.

If the porosity exceeds 90%, the water droplets dispersed in the solvent will pass through the fiber structure, resulting in poor separation accuracy of the water droplets, and the porosity will decrease due to the fiber structure settling. There is a problem in that the liquid permeation rate changes significantly. In addition, if it is less than 3°, it is virtually impossible to obtain an industrially usable liquid permeation rate. The porosity of the fibrous structure is preferably in the range of 40 to 80 inches.

The thickness of the fibrous structure is not limited at all, and may be set to a thickness that provides the desired permeation rate.

Usually, it is used in the range of 0.05 to lor+g.

In the method of the present invention, there are no limitations on how to incorporate the filter (-) into the specific gravity separation step. This filter (a) is preferable because it can be incorporated into the specific gravity difference separator using existing equipment, so that the equipment does not become large. For devices equipped with two or more specific gravity difference separators, it is preferable to incorporate a filter on the downstream side in terms of load (life) on the filter.

The shape of the filter is not limited in any way, and it can be used in any shape such as a flat membrane, cylindrical, tubular, spiral, or rosette, but from the viewpoint of processing efficiency, a glossy rosette is preferable. It is preferable to use

For the filter used in the method of the present invention, it is also possible to use a reinforcing material such as a wire mesh or a mesh-like 7-piece for the purpose of reinforcement. Furthermore, in order to collect the nighttime garbage to be separated, it is also possible to use a dust-collecting material as a pre-filter before treating the liquid to be separated with the filter. Specifically, examples of the pre-filter include a film-like or cotton-like dust-trapping material.

The method for recovering the solvent in the method of the present invention is not particularly limited, and various filtration methods such as patch type or continuous type, vertical type, horizontal type, multistage type, etc. can be applied.

A specific example of how the filter is incorporated in the method of the present invention is shown in FIGS. 4 and 5. The water/solvent mixture 21 flowing into the specific gravity difference separator 19 from the water/solvent mixture 21 is separated into a solvent and water by the sheet filter 20 or filter element 25 used in the method of the present invention. That is,
Only the solvent permeates through the filter, and the permeated solvent is led to the solvent recovery outlet 23. Water 22 separated by filter 20 or 25 is discharged from water outlet 24.

〔Effect of the invention〕

According to the method of the present invention, free water mixed in the recovered solvent can be separated efficiently and with high precision.
Various troubles caused by the contamination of free water can be prevented.

[Smile II] Next, the present invention will be specifically explained with reference to the following examples. In the following examples, the water concentration was measured using a Karl Fischer moisture meter iKc-3P manufactured by Kyoto Electronics Industry Co., Ltd. Furthermore, the size of water droplets dispersed in the solvent was measured using optical micrographs.

Example 1 Six types of fiber structures made of polyethylene terephthalate fibers having a single fiber diameter of 0.5 to 15.6/+m were molded.

A 2F4 fiber structure (porosity 75%, thickness 0.17 mm) with a single fiber diameter of 0.5 and a length of 711 m was obtained by melt blowing. Also, single fiber diameter 3.5-15.6 μm
The four types of fiber structures were obtained by directly cutting the fibers obtained by the spinning method into five lengths, and then using the wet papermaking method. The fiber structures having different single fiber diameters thus obtained were subjected to a water repellent treatment under the following conditions.

Processing conditions: Processing agent, POLON-MR (Shin-Etsu Chemical System),
CAT-LZ (Shin-Etsu Chemical) Concentration 4% by weight Dry at 100°C x 3 minutes Heat treatment 170°C x 1 minute Pad dry cure method Filters with different single fiber diameters obtained in this way are shown in Figure 6. 26 elements of the same type (transmission area 0.15 m2) were installed in the specific gravity difference separator of a dry cleaner MC-9 manufactured by Mitsubishi Permac Co., Ltd. in the manner shown in FIG. -10,000, Tetrachlorethylene 501 and activator Gungu Clean P were in the distiller of a dry cleaner machine.
M250 (% by Dai-Kogyo Seiyaku Co., Ltd.) cc and 31 cc of water were added and distilled at a rate of 0.51/min to separate free water in tetrachlorethylene in a specific gravity difference separator.

After distillation and subsequent cooling, the solvent was a cloudy liquid with water droplets dispersed in tetrachlorethylene.

When we measured the water content in tetrachlorethylene, we found that
The size of the water droplets was photographically measured at 35° C. and 250 p, p, m using an optical microscope and found to be 0.5 to 3 μm.

Table 1 shows the measurement results of the water content in tetrachlorethylene after passing through various filters. Comparative Example (3) in Table 1 shows the results obtained when processing was performed using a conventional method without installing a filter in the specific gravity difference separator.

It is clear from the results of No. 1 that the method of the present invention has an extremely good separation performance between the solvent and free water, and completely traps and separates water up to the level of solubility. Comparison 1
As is clear from the results of 1fJ(3), it is found that in the conventional method, finely dispersed water droplets cannot be separated only by the specific gravity difference separation process.

Margin below *The saturated water concentration of gloss chlorethylene at 25°C is approximately 100 p, p, m.

**The water pressure resistance of Examples (1) to (4) according to the JISL-1092B method was all 1OOtnx+H20 or higher.

Example 2 A single fiber with a diameter of 21 μm and a thickness of 0.
A polypropylene nonwoven fabric with a porosity of 95q6 was obtained.

Next, this nonwoven fabric is pressed to have a porosity of 21 to 95 cm.
Six types of arrogant nonwoven fabrics were created. In other words, the pressing process is 1
~150ψ, etc., and in addition to this, a nonwoven fabric was created in which the porosity varied depending on the pressing temperature and time. Next, several layers of nonwoven fabric with the same porosity are layered to reduce the thickness to 0.
．． A fiber structure made of 25 steel was created.

The six types of fiber structures thus obtained were subjected to water repellent treatment in the same manner as in Example 1.

The filter after the water repellent treatment was installed in the specific gravity difference separator of a dry cleaner MC-9 manufactured by Mitsubishi Permac Co., Ltd. in the same manner as in Example 1. On the other hand, put 501 parts of trichloroethane and 2 parts of water in the distiller of a dry cleaner machine, and
Distillation was carried out at a rate of 1/min, and an experiment was conducted to separate free water in trichloroethane in a density difference separator.

Distillation - Weighing water in trichloroethane after cooling 510
The size of the microscopic water droplets was 0.5 to 3 tzm as a result of photomicrograph measurements.

The experimental results are shown in the second column.

As is clear from the results shown in Table 2 below, it can be seen that the method of the present invention has an extremely good separation performance of free water in the solvent and a high liquid permeation rate.

A filter with a porosity exceeding 90% has poor water separation accuracy. In the case of a filter with a porosity of less than 30 mm, the liquid permeation rate is extremely low, and its industrial utility value is low.

Example 3 Single fiber diameter 1.5 μm, thickness 0 by melt blowing method
．． A polyethylene terephthalate nonwoven fabric with a length of 17 m and a porosity of 75 inches was made. Using this nonwoven fabric, water repellency treatment was performed under the following conditions and method to produce filter tendrils (,) to (c).

(,) Same process as Example 1 (b) Same process as Implementation Project l (However, POLON
-kiR.

CAT LZ) Concentration is l/20) (c) No water repellent treatment The filters of (&), (b), and (c) above were processed in the same manner as in Example 1 using Mitsubishi Notarmac Dry Cleaner MC-9. It was installed in the specific gravity difference separator of the machine.

On the other hand, 501 ml of tetrachlorethylene and 31 ml of water were placed in the distiller of a dry cleaner machine and distilled at a rate of i/min, and an experiment was conducted to separate free water in tetrachlorethylene in a specific gravity difference separator. .

The recovered solvent after separation is collected in a clean tank, and when the tetrachlorethylene in the distiller is exhausted, water 31 is put into the distiller again separately from the solvent 501 in the clean tank.
A continuous test was conducted for 10 hours.

The solvent used after distillation and subsequent cooling was a cloudy liquid in which water droplets were dispersed in tetrachloroethylene, and the water content was 240 ppm at 37°C. The size of water droplets is 05~
It was 5 μm.

The experimental results for filters (body), (b), and (e) are shown in the third precept.

As is clear from the results in Table 3 below, it can be seen that the method of the present invention under the conditions of the example shows good separation performance even after 10 hrs have elapsed. On the other hand, the water pressure is 50 tea
It can be seen that the H2O filter cannot completely separate free water.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a dry cleaning machine, Figure 2 is a system diagram of a precision washing machine, and Figure 3 is a system diagram of a solvent recovery device. FIGS. 4 and 5 show a specific example of how to incorporate a filter into a specific gravity difference separator. FIG. 6 shows the appearance of the filter element used in the example.

Claims (1)

[Claims] 1. In the method of separating solvent and water by specific gravity separation process, single fiber diameter 0.1 to 10μ is used in the specific gravity separation process.
1. A method for recovering a solvent, which comprises incorporating a filter made of a water-repellent fibrous structure mainly composed of fibers having a porosity of 30 to 90% to selectively allow the solvent to pass therethrough.