JPH0674525B2 - Method for circulating cleaning liquid of polymerization equipment - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a cleaning method by circulating a cleaning liquid for cleaning the inside of a polymerization apparatus.

[Prior art and its problems]

Conventionally, cleaning of the inner surface of an apparatus for performing polymerization or an apparatus for performing polymerization and spinning is often performed for the purpose of removing scale, and a cleaning method utilizing dissolution or decomposition action mainly with an acid, an alkali, or a solvent is used. There is.

However, acid cleaning and alkali cleaning cannot avoid the problem of corrosion of the equipment material, and solvent cleaning does not reach the target cleaning level simply by repeatedly feeding and discharging the solvent.

On the other hand, as precision cleaning often performed in the semiconductor field and the like, there are steam cleaning, ultrasonic cleaning and the like, but there are many unsatisfactory aspects and they are not sufficient.

For example, in vapor cleaning, since a method of evaporating by heating and condensing by lowering the temperature is adopted, the dissolving power of organic substances is small, and the cleaning efficiency is extremely poor in view of the time and energy required for evaporation.

In addition, the ultrasonic cleaning method has a problem that the vibrator needs to be inserted inside, and even if the vibrator can be inserted inside, it is extremely difficult to uniformly clean the inner surface of the device due to the property of the vibrator. Further, a method in which a vibrator is brought into contact with the outer wall of the device is conceivable, but this also has many difficult problems such as resonance, contact surface shape, and mounting method.

On the other hand, however, in the production of high-purity polymers and transparent polymers, there has been a strong demand for precision cleaning of the inner surface of the device.

For example, polymers that are characterized by transparency include polycarbonate with excellent heat resistance, polystyrene with high versatility,
Also, in terms of transparency and weather resistance, polymethylmethacrylate,
In the case of an optical fiber, of which transparency is the most important factor, the removal of dust mixed in the core polymer to be the optical path is extremely important.

FIG. 1 illustrates a conventional washing device for a polymerization spinning device. Reference numeral 1 is a polymerization spinning device, 2 is a washing liquid storage tank, and 3 is a washing liquid filtering device equipped with a microfilter. The polymerization spinning device 1 and the cleaning liquid storage tank 2 are connected by a pipe 4 via a three-way cock switching cock 5, and the cleaning line can be switched to a monomer supply line by a switching operation of the three-way cock 5.

A N ₂ gas supply line 6 and a vacuum line 7 are connected to the upper part of the cleaning liquid storage tank 2, and after the cleaning liquid storage tank 2 is depressurized by the vacuum line 7, the cleaning liquid is filtered under reduced pressure by a microfilter to obtain a filtrate. Can be stored in 2.

A decompression line 10 and a pressurization line 11 are connected to the upper part of the polymerization spinning device 1 via a pipe 8 and a three-way cock pressure adjustment valve 9 for adjusting pressurization / decompression. Note that 13 is a pipe joint.

To send the cleaning liquid stored in the cleaning liquid storage tank to the polymerization spinning device 1, the valve 12 provided at the lower part of the polymerization spinning device is closed, and then the inside of the polymerization spinning device is depressurized by the vacuum line 10, and then the cleaning liquid storage tank 2 is filled with N ₂ It is performed by applying pressure through the gas line 6.

After the transfer is completed, the switching cock 5 and the pressure adjusting valve 9 are closed to seal the inside of the polymerization spinning device, and then the device main body is heated to heat and wash the inside of the device.

When the valve 12 is opened immediately after the washing is completed, the washing liquid is discharged by the vapor pressure of the washing liquid sealed inside the polymerization spinning device. Then, this operation is repeated a predetermined number of times.

However, in the case where the cleaning is repeatedly performed by the conventional method, the transferred cleaning agent is instantly evaporated when the polymerization spinning device is in a heated state, and a reverse pressure is generated by the vapor pressure of the cleaning agent to stop the transfer. Not only that, but in extreme cases, it is expected that the back pressure will reach the storage tank and cause a dangerous condition. For this reason, there is a problem in that heating and cooling of the polymer spinning device must be repeated in repeating washing, and the washing efficiency is extremely poor.

Further, in the case of the conventional cleaning device, there is a problem that it is extremely difficult to clean the line communicating with the polymerization spinning device, for example, the pressurizing / depressurizing line. In other words, the low molecular weight components that spread out from the polymerization spinning device during the previous polymerization are often deposited thinly inside the piping of the communicating line, which is finely cracked and broken due to subsequent thermal changes, etc. There is a problem that the foreign matter appears as a foreign substance and is fed into the apparatus when N ₂ gas is fed.

[Purpose of the present invention]

It is an object of the present invention to provide a cleaning method capable of improving various drawbacks of the prior art and capable of precisely cleaning the inner surface of a polymerization apparatus.

[Configuration of the present invention]

 That is, the present invention has the following configurations.

(1) A pipe for circulating a cleaning liquid is provided between a polymerization device equipped with a pressurization / decompression adjusting line and a cleaning liquid storage tank, and a cleaning liquid is supplied to a cleaning liquid supply line for supplying the cleaning liquid from the cleaning liquid storage tank to the polymerization device. Of the inside of the polymerization apparatus by a cleaning solution circulation cleaning apparatus in which a microfilter having a pore size of 0.5 μm or less is installed, and a looking glass is installed in a cleaning solution recovery line for recovering the cleaning solution from the polymerization apparatus to the cleaning solution storage tank. A cleaning liquid circulating cleaning method for a polymerization apparatus, wherein the cleaning liquid is heated and circulated with a cleaning liquid made of an organic solvent.

(2) A cleaning liquid circulation in a polymerization apparatus according to claim 1, wherein a bypass circuit is provided, one end of which is connected to the pressurization / decompression adjustment line and the other end of which is connected to the cleaning liquid recovery line. Cleaning method.

The circulation cleaning device used in the method of the present invention is used for cleaning the inner surface of a device in which a polymerization reaction is carried out, a so-called polymerization device. This polymerization apparatus may be an apparatus that also serves as melt spinning of the polymer obtained by the polymerization reaction, that is, a so-called polymerization spinning apparatus.

Hereinafter, description will be given with reference to FIG. 2 showing one embodiment of the apparatus when the method of the present invention is applied to washing of a polymer spinning apparatus. FIG. 2 is preferable when the cleaning liquid circulation cleaning is performed in a closed system in the polymerization spinning device, and the reference numerals indicate the same or corresponding members.
In FIG. 2, 14 is a cleaning liquid supply line connecting the upper end of the polymerization spinning device and the cleaning liquid storage tank 2, 15 is a cleaning liquid recovery line connecting the lower part of the polymerization spinning device 1 and the cleaning liquid storage tank 2, and the supply line is the cleaning liquid storage tank 2 And a polymerization spinning device 1, which are sequentially arranged between the liquid delivery pump 16, the filter 17, the three-way cock 5, and the pipe 4 and the pipe joint 13 that connect these components to each other. The recovery line 15 is a polymerization spinning device. 1 and a cleaning liquid storage tank 2 are sequentially provided with a valve 12, a looking glass 18, a pipe joint 13 ', a three-way valve 19 and a pipe 4'.

A pressurizing / depressurizing pipe 8 connected to the upper end of the polymer spinning device 1.
Is connected to a 4-way branch pipe 20, one branch pipe is a 3-way cock
The second branch pipe is connected to the depressurization line 11 via the valve 21, the second branch pipe is connected to the pressurization line 11 via the valve 22, and the third branch pipe is connected to the valve 12 and the looking glass 18 via the valve 23 and the pipe 24. Is connected to the recovery line between. That is, the pipe 8, the 4-way branch pipe 20, the valve 23, and the pipe 24 form a bypass circuit 25.

Next, in order to carry out the circulation cleaning with the cleaning liquid by this apparatus, first, the cleaning liquid which has been sufficiently refined chemically is put into the storage tank 2 and is fed by the liquid feed pump 16 to the filtration device 17 equipped with a micro filter for pressure filtration.

The cleaning liquid is further passed through the three-way cock 5 and sent to the polymerization spinning device 1.

In this case, in order to fully fill the polymerization spinning device with the cleaning liquid, the valves 12, 22, 23 are closed and the valve 21 is opened to the atmosphere, and the liquid feeding is continued until the cleaning liquid overflows.

When the cleaning liquid overflows from the atmosphere opening port, the valve 21 is closed, the valve 12 is opened, and the three-way valve 19 is set on the circulation circuit side, whereby the circulation cleaning can be started.

When only the bypass circuit 25 is washed, it can be easily performed by closing the valve 12 and opening the valve 23.

Of course, it is also possible to wash the polymerization spinning device and the bypass circuit at the same time.

When the circulation cleaning is started, the heating device 26 of the polymerization spinning device is gradually heated to a predetermined temperature to start the heating circulation cleaning.

In addition, in this device, there is a concern that a blind hole is formed between the branch point of the 4-way branch pipe connected to the pipe 8 and the valve 21 or 22 to cause poor cleaning. Therefore, for any polymer such as polymethylmethacrylate, polystyrene, or polycarbonate. In the case of, the cooling part is provided between the polymerization spinning device and the four-way branch points so that the boiling point is not more than the boiling point under these conditions, or the space between them is set to a sufficiently large value to allow natural heat dissipation, and then Therefore, it is desirable to consider that low molecular weight components do not adhere.

Further, in the present invention, as a means for improving the cleaning efficiency, the inside of the cleaning system may be an open system.

That is, the temperature of the heating device attached to the polymerization spinning device is made equal to or higher than the boiling point of the cleaning liquid in the atmosphere, and a part of the system, for example, the cleaning liquid storage tank is opened to cause boiling of the cleaning liquid inside the polymerization spinning device. The bubbling effect makes it possible to wash the inner surface of the polymerization spinning device more efficiently.

FIG. 3 shows an example of an open type cleaning liquid storage tank, in which (a) is provided with an opening 2'that horizontally closes the storage tank and extends horizontally to the atmosphere due to the vapor discharge of the cleaning liquid. It is possible to prevent dust from entering.

In FIG. 3B, a downward opening portion 2 ″ is provided on the side surface in order to more completely prevent the entry of dust from the outside.

In the present invention, the pipe joint connecting the respective elements of the cleaning device is also very important from the problems of airtightness and dust generation,
If airtightness is poor, dust will be reliably taken in from the outside of the system, and conversely, if airtightness is mainly considered, problems with the material (dust generation) will occur, so caution is required.

The microfilter used in the present invention is a membrane type absolute filtration type filter having a pore size value by mercury porosimeter of 0.5 μm or less, preferably 0.2 μm or less. Applicable ones are cellulose ester, polyolefin and polytetrahydrofuran. Although there are fluoroethylene, polycarbonate, polyamide and the like, polytetrafluoroethylene is most preferable from the viewpoint of chemical resistance and heat resistance.

Further, the circulation direction of the washing liquid can be either from the bottom to the top of the polymerization spinning device (not shown) or from the top to the bottom (FIG. 2).

The evaluation of the cleanliness level of the inner surface of the washed polymerization spinning device was expressed by irradiating a halogen lamp with a light source narrowed with a lens system to the looking glass provided immediately after the exit of the polymerization spinning device for sampling without taking it out of the system. This can be done by observing the bright spots that

According to the present invention, the evaluation of the cleaning level can be carried out simultaneously during the cleaning operation, and the method can be carried out until the observed bright spot becomes completely 0 per 10 cm optical path.

After cleaning, use the valve to completely remove the cleaning solution.
Only valve 12 and valve 23 are open, all others are closed and valve 19
To the discharge side (lower side in FIG. 2) and the cleaning liquid is discharged by vapor pressure. Then immediately close valves 12, 23,
The valve 21 is switched to the vacuum line 10 side, and vacuum drying is performed at a vacuum degree of 1 to 10 ^-2 Torr to completely remove organic substances and dust from the inner surface of the polymerization spinning device.

The cleaning liquid applied in the present invention includes methyl methacrylate, esters such as methyl acetate, acetone,
Ketones such as methyl ethyl ketone, hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene and toluene, ethers such as methyl cellosolve and ethyl ether, and organic solvents such as alcohols such as methyl alcohol and ethyl alcohol. It is selected and used in consideration of solubility with respect to polymer, boiling point, evaporation rate and the like.

If a large amount of polymers and other organic substances remain in the polymerization spinning device, repeat the operation of temporarily storing the cleaning liquid in the polymerization spinning device and then discharging it, and heat the mixture until the concentration of the polymer and organic substances is at least 0.1% or less. Circulating cleaning is preferable from the viewpoints of equipment maintenance and cleaning efficiency.

In the above description, the circulation cleaning device of the polymerization spinning device has been described, but the circulation cleaning device of the present invention can of course be applied to a device that only performs polymerization, and particularly produces a high-purity polymer or a transparent polymer. It is useful for cleaning the inner surface of polymerization equipment.

[Effects of the Present Invention] The present invention configured as described above has a remarkable practical effect that the cleaning efficiency is extremely excellent and precision cleaning of the inner surface of the apparatus can be performed reliably and completely.

Hereinafter, the effects of the present invention will be specifically described with reference to examples.

Example 1 An open heating cleaning was carried out by the apparatus shown in FIG.

The material of the cleaning liquid storage tank was stainless steel, and the liquid feed pump used was a gear pump (manufactured by Iwaki Co., Ltd.) in which the material in contact with the liquid consisted only of tetrafluoroethylene and stainless steel.

The microfilter has a mercury porosimeter value of 0.
A tetrafluoroethylene membrane filter (manufactured by Sumitomo Electric Co., Ltd.) having a pore size of 1 μm was loaded into a stainless steel filter holder and used.

The pipes that make up the cleaning system use tubes made of tetrafluoroethylene perfluorovinyl ether, and the joints at the connection are "Sagelock" (Sagelock
Manufactured by Company) was used.

Acetone for electronic industry (Kanto Chemical Co., Ltd.)
The cleaning liquid fed by the liquid feed pump was once stored in the polymerization spinning device, and then the polymerization spinning device and the bypass circuit were simultaneously flown to start circulation cleaning. The heating device of the polymerization spinning device was heated to 80 ° C., and heating and circulation washing was continuously performed for 3 hours.

The results were extremely excellent as shown in Table 1.

In addition, as a result of collecting this cleaning liquid and performing an inorganic analysis, no increase was observed from the blank product even in the PPb order.

Comparative Example 1 The apparatus shown in FIG. 1 was used as the cleaning apparatus, and the cleaning solution storage tank, microfilter, piping pipe, and cleaning solution were used in Example 1.
The same as was used. Also, as a pipe joint, "Sagelock" (made by Swagelock Company)
It was used.

The cleaning liquid was transferred by vacuumizing the polymerization spinning device, pressurizing the cleaning liquid storage tank with N ₂ gas at about 0.5 kg / cm ² , and transferring the cleaning liquid by the pressure difference.

The washing liquid was heated to 130 ° C. in the main body of the polymerization spinning device, washed for 30 minutes, and then discharged.

Subsequently, the main body of the polymerization spinning device was cooled for 30 minutes so that the cleaning liquid could be transferred.

The results of repeating this operation 16 times are shown in Table 1, but they were completely unsatisfactory.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a conventional cleaning device, FIG. 2 is a schematic diagram illustrating the cleaning device of the present invention, and FIG. 3 is a schematic diagram illustrating an open-system cleaning liquid storage tank used in the present invention. 1: Polymerization spinning device 2: Cleaning liquid storage tank 17: Filtration device 18: Looking glass 14: Cleaning liquid supply line 15: Cleaning liquid recovery line 25: Bypass circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-46350 (JP, A) JP-A-51-50885 (JP, A) Actually opened 54-75068 (JP, U) Actual-opened 57- 111381 (JP, U)

Claims (2)

[Claims] 1. A pipe for circulating a cleaning liquid is provided between a polymerization device equipped with a pressurization / decompression adjusting line and a cleaning liquid storage tank,
A cleaning liquid recovery line for supplying the cleaning liquid from the cleaning liquid storage tank to the polymerization device is provided with a microfilter having a pore size of 0.5 μm or less for filtering the cleaning liquid, and the cleaning liquid recovery from the polymerization device to the cleaning liquid storage tank. A cleaning liquid circulation cleaning method for a polymerization device, wherein the inside of the polymerization device is heated and circulatingly cleaned with a cleaning liquid composed of an organic solvent by a cleaning liquid circulation cleaning device having a line of a looking glass. 2. A polymerization apparatus according to claim 1, further comprising a bypass circuit, one end of which is connected to the pressurization / decompression adjustment line and the other end of which is connected to the cleaning liquid recovery line. Cleaning solution circulation cleaning method.