JPH09150002A - Refining method for silicone oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently refine a silicone oil by continuously and efficiently removing unnecessary and unreacted substances with a low molecular weight and oligomer substances with a low molecular weight to a highly pure degree. SOLUTION: A silicone oil having the general formula (R1 and R2 stand for same or different monovalent hydrocarbon groups or hydroxyl, R3 and R4 for same or different monovalent hydrocarbon groups, (n) for integer between 100-300) is continuously brought into contact and mixed with an extraction solvent in a supercritical state in which the temperature and the pressure exceed the critical values which a substance characteristically has or a subcritical state in which either the temperature or the pressure exceeds the critical value which a substance characteristically has and then the resultant mixed fluid is released to and dispersed in an extractor which is previously filled with the extraction solvent in the supercritical state or the subcritical state to extract and remove substances with a low molecular weight contained in the silicone oil to the extraction solvent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying silicone oil for obtaining high-quality silicone oil.

[0002]

2. Description of the Related Art Silicone oil made of dimethylsiloxane polymer is used as a raw material for potting agents for electronic devices, molding agents, lubricants, coating agents and the like. However, since generally produced silicone oil contains unreacted low-molecular-weight dimethylsiloxane and oligomer low-molecular-weight substances, if these impurities are not removed sufficiently, it is necessary to remove these impurities for electronic devices. When used as a substrate or the like, the low molecular weight substance bleeds out of the silicone product, causing failure such as contact failure of electronic equipment.

Therefore, it has been conventionally practiced to remove these low molecular weight substances to purify the silicone oil. Conventionally, the method for purifying the produced silicone oil is distillation under atmospheric pressure or reduced pressure. The thin film evaporation method and the like are employed, and these methods are appropriately selected or combined.

However, the residual concentration required value of the low molecular weight substance is decreasing year by year, and the content of unreacted low molecular weight substance or oligomer low molecular weight substance which is an unnecessary component in the product is removed to a desired value. In order to achieve this, the operating pressure and temperature must be maintained under extremely severe conditions, and in this respect, deterioration of the product and increase in the cost of the purification process have become problems. There is a need for an effective refining method for efficiently and inexpensively removing to the level that does not cause a failure such as contact failure.

Further, in the above conventional separation and removal treatment, the purification concentration is limited even if the purification is repeated a plurality of times or the residence time is extended, and a new purification method having a high separation ability is also desired. Was there.

By the way, in recent years, a supercritical fluid extraction separation method using a fluid in a supercritical state as a solvent has been attracting attention as a method for extracting a trace amount of components, and its application example has been reported for the purification of silicone oil. . For example, Japanese Examined Patent Publication No. 54-10539 discloses a method of dissolving a substance such as silicone oil in a supercritical fluid and extracting only necessary components. However, a conventionally known method, for example, charging silicone oil into an extractor and pouring an extraction solvent in a supercritical state from above, below or from the side into the extractor,
When an extraction separation method that causes contact with silicone oil is used, the removal of low molecular weight substances from silicone oil has a small surface area because silicone oil does not easily form droplets, and surface renewal does not occur easily. Further, the fluid in the supercritical state is difficult to diffuse into the silicone oil, and the mass transfer does not effectively occur, so that the removal of the low molecular weight substance was insufficient.

[0007] Further, a method of mounting a stirring device to effectively disperse and contact the liquid is used.
Sufficient effects were not obtained for higher viscosity high molecular weight silicone oil and the like. Therefore, it has not been applied to industrialization in this field related to silicone oil.

[0008] The present invention has been made in view of the above circumstances,
A method for purifying a silicone oil using a supercritical fluid or an inert fluid in a subcritical state. Particularly, even a highly viscous silicone oil can be refined satisfactorily, efficiently, and inexpensively to a high purity, which corresponds to industrialization. Provide a way that can be.

[0009]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies for achieving the above-mentioned object, the present inventor removed a low molecular weight substance in a silicone oil represented by the following general formula (1). In the case of refining the silicone oil, the extraction solvent in the supercritical state in which the temperature and the pressure exceed the critical value specific to the substance or in the subcritical state in which one of the temperature and the pressure exceeds the critical value specific to the substance is used. By contact-mixing with, and then continuously dispersing, preferably in a jet or atomized state, the mixed fluid into an extractor (purifier) filled with an extraction solvent in a supercritical state or a subcritical state, preferably by jet dispersion. Unnecessary low molecular weight substances (unreacted low molecular weight substances and oligomers low in the silicone oil contained in the supercritical or subcritical fluid atmosphere set to a predetermined temperature and pressure). Molecular weight substances) are preferentially dissolved and extracted, separated and purified from higher molecular weight silicone oils, and relatively high molecular weight silicone oils obtained by separating unreacted low molecular weight substances and oligomer low molecular weight substances are extracted by the extractor. (Purifier) Recovered from the bottom, while the low molecular weight substance is entrained in the supercritical or subcritical fluid and discharged to the outside of the extractor, whereby it is contained in the silicone oil by the continuous supercritical fluid. It was found that unnecessary low molecular weight substances can be extracted and separated.

[0010]

Embedded image (In the formula, R ¹ and R ² are the same or different monovalent hydrocarbon groups or hydroxyl groups, R ³ and R ⁴ are the same or different monovalent hydrocarbon groups, and n is an integer of 100 to 3000. It is.)

More specifically, before introducing the silicone oil to be purified into the extractor, a solvent in which the temperature and pressure are in a supercritical state in which the temperature and the pressure exceed the critical value, or in which either the temperature or the pressure is in the critical state, and the silicone oil By mixing and to form a mixed fluid with reduced viscosity, and discharging this mixed fluid into the extractor, the silicone oil becomes minute droplets, which eliminates the need for a stirrer and produces these droplets. Since the silicone oil is mixed with the solvent in which the temperature and the pressure pre-filled in the extractor exceed the critical value in the supercritical state or the temperature or the pressure is in the critical state, the silicone oil and the solvent It has been found that the surface contact can be made smoothly, low molecular weight substances can be easily dissolved, and desired silicone oil can be recovered well. Which has led to eggplant.

Therefore, according to the present invention, a silicone oil represented by the following general formula (1) is used in a supercritical state in which temperature and pressure exceed a critical value peculiar to a substance, or either one of temperature and pressure is a critical peculiar to the substance. The extraction solvent in a subcritical state exceeding the value is continuously contact-mixed, and then the mixed fluid is
The extraction solvent in the supercritical state or the subcritical state is discharged and dispersed in an extractor which is previously filled, and the low molecular weight substance contained in the silicone oil of the following formula (1) is extracted and removed in the extraction solvent. A method for purifying a silicone oil is provided.

[0013]

Embedded image (In the formula, R ¹ and R ² are the same or different monovalent hydrocarbon groups or hydroxyl groups, R ³ and R ⁴ are the same or different monovalent hydrocarbon groups, and n is an integer of 100 to 3000. It is.)

As described above, in order to remove the unreacted low molecular weight substance or oligomer low molecular weight substance contained in the silicone oil, conventionally, distillation under atmospheric pressure or reduced pressure, or separation by a thin film evaporation method or the like is performed. However, these methods consume a large amount of energy due to heating of equipment, and further, there is a limit in the removal level of the low molecular weight substance. Naturally, the lower limit of the concentration of the remaining low molecular weight substance in the silicone oil has been pursued by the combination of the above-mentioned distillation method and the evaporation method and the repeated operation, but it was not a rational process due to the complicated process and equipment.

On the other hand, according to the method of the present invention, if a fluid having a critical point near room temperature is selected as an extraction solvent in advance, for example, carbon dioxide, as compared with the conventional distillation method and evaporation method, the temperature is around room temperature. Since it can be refined, the amount of energy consumed by heating is very small, which is a gain.

The removal level of the above low molecular weight substances is also
Although it depends on the degree of polymerization and the viscosity of the silicone oil, the conventional distillation method and evaporation method, and the purification method using a supercritical fluid known in Japanese Patent Publication No. 54-10539. As such, if a stirring device is provided in the extractor to stir, or if the mixture to be separated and the supercritical fluid are brought into direct countercurrent contact to increase the extraction efficiency, a higher molecular weight substance, For example, the degree of polymerization n in the above general formula (1)
About 1000 pp for highly viscous materials with a value of 1500 or more
The lower limit was about m. This is because the contact between the supercritical fluid and the extraction raw material in the conventional supercritical fluid extraction separation method, etc.
Dispersion was caused by mechanical stirring means or direct collision of both substances, but this method is because uniform dispersion hardly occurs, and renewal of the contact surface does not proceed.

On the other hand, according to the method of the present invention, the contact between the final supercritical or subcritical fluid and the extraction raw material releases the extraction raw material or the solution containing the raw material into the supercritical or subcritical fluid atmosphere. Since it is dispersed, preferably discharged from a fine nozzle to form a jet or atomized state, it is uniformly dispersed as fine droplets, and the diffusion of the supercritical or subcritical fluid to the raw material is accelerated. In particular, when a highly viscous silicone oil is used as the raw material, mixing the supercritical or subcritical fluid with the silicone oil lowers the viscosity, so the liquid column flowing out from the nozzle is broken and becomes droplets. It has the advantage of being easy. The diffusion method by this release makes the dispersion of silicone oil from low molecular weight to high molecular weight extremely uniform, and has a higher purity than the conventional method, specifically, without being influenced by the polymerization degree and the viscosity of the silicone oil. Is capable of removing unreacted low molecular weight substances and oligomer low molecular weight substances up to about 50 ppm.

The present invention will be described in more detail below. The present invention relates to a method for purifying a silicone oil represented by the following general formula (1).

[0019]

Embedded image

Here, R ¹ and R ² are the same or different, substituted or unsubstituted monovalent hydrocarbon groups or hydroxyl groups,
As the monovalent hydrocarbon group, an alkyl group having 1 to 10 carbon atoms,
Examples thereof include an alkenyl group, an aryl group, an aralkyl group, and a halogen-substituted monovalent hydrocarbon group thereof, but a methyl group and a phenyl group are common. Also, R ³
And R ⁴ are the same or different from each other, a substituted or unsubstituted monovalent hydrocarbon group, and the monovalent hydrocarbon group is the same as described above.

N is an integer of 100 to 3000, preferably 500 to 3000, more preferably 1000 to
The present invention is preferably applied to a silicone oil having a viscosity of 3000 and a viscosity at 25 ° C. of 5000 cp or more.

The impurities (low molecular weight substances) to be removed from the silicone oil are usually the following general formula (2):
And a non-cyclic organopolysiloxane represented by the following general formula (3).

[0023]

Embedded image (However, R ^{1 to} R ⁴ have the same meanings as above, and m is 3 to
It is an integer of 20. )

In the present invention, first, the silicone oil is continuously contact mixed with the extraction solvent in the supercritical or subcritical state. Here, carbon dioxide having a critical temperature peculiar to the substance in the vicinity of room temperature is preferably selected as the extraction solvent in consideration of running cost and energy consumption accompanying heating. The critical temperature of carbon dioxide is 31 ° C. and the critical pressure is 72.80 atm.

The continuous contact mixing of the silicone oil and the extraction solvent may be a mixing tank equipped with a stirrer or mixing in a pipe. Mixing in the pipe is advantageous in that it does not have large equipment. In this case, simple pipe mixing may be used, but in order to mix more uniformly, a line mixer is installed, or supercritical or subcritical fluid or silicone oil is jetted with a nozzle having a fine bore to mix. It is desirable to do. This also causes some preliminary extraction in the pipe. The mixing amount of the extraction solvent for the silicone oil, when will depend on the solubility of the extraction solvent used, using CO _2, silicone oil 1
On the other hand, a flow rate of 2 times or more (weight ratio) is preferable.

Then, the above formula (1) preliminarily contact-mixed is used.
The silicone oil and the extraction solvent are continuously discharged into an extractor filled with the extraction solvent in a supercritical or subcritical state in advance and uniformly dispersed. In this case, the former and latter extraction solvents are the same fluid, but one or both of temperature and pressure may be different. Regarding the temperature and pressure at the time of contact mixing which is performed in advance and at the time of discharging to the extractor, it is better that the temperature is lower and the pressure is higher during the contact mixing. This is because the supercritical or subcritical fluid contained in the liquid column that has flowed out of the nozzle when discharged to the extractor expands, which facilitates the formation of fine droplets and increases the extraction efficiency. . Further, in the case of continuously discharging the solution containing the silicone oil that has been contact-mixed in advance into the extractor, it is preferable to discharge it in a jet or spray state from a nozzle having a fine diameter, but the linear velocity at the nozzle outlet is It is set to 0.1 m / s or more, preferably 0.5 to 6 m / s. Further, the inner diameter of the nozzle is preferably 0.2 to 3 mm. At this time, the solution is in the form of minute droplets having an increased surface area and moves in the extractor while contacting with the supercritical fluid that is the extraction solvent. By discharging the mixed fluid into the extractor in this way, unreacted low molecular weight substances and oligomer low molecular weight substance components are extracted during jetting from the nozzle and during movement in the extractor to purify the silicone oil. To be done.
The extraction solvent in the extractor can be countercurrent or cocurrent with the silicone oil-containing solution discharged into the extractor, but it effectively causes fluid contact and mass transfer. Countercurrent is preferred for this.

The unreacted low molecular weight substance or oligomer low molecular weight substance dissolved in the extraction solvent in the extractor is separated from the higher molecular weight silicone oil and discharged out of the system together with the extraction solvent. The low molecular weight substance discharged out of the system is
Transfer to at least one separator connected to the extractor and separate from the extraction solvent. The separated and recovered extraction solvent can be used again in the present purification step, and in the present purification method in which a large amount of the extraction solvent is consumed, recycling and recycling is economically advantageous.

On the other hand, the higher molecular weight silicone oil from which the above low molecular weight substances have been removed is recovered from the bottom of the extractor.

By carrying out the above operation continuously or intermittently, unnecessary low molecular weight substances such as unreacted low molecular weight substances and oligomer low molecular weight substances from silicone oil can be efficiently and highly purifiedly removed. it can.

FIG. 1 is a flow chart showing a preferred embodiment of the present invention, in which 1 is a silicone oil supply pipe 1a.
A silicone oil storage tank 2 having a carbon dioxide supply pipe 2a, a carbon dioxide storage tank 3 having a carbon dioxide supply pipe 2a, and an extractor (refiner) 3 having a lower portion of the silicone oil storage tank 1 and an upper portion of the extractor 3. 4 is connected by a silicone oil transport pipe 5 and one end of the transport pipe 5 at the position between the pump 4 and the extractor 3 is connected to the lower portion of the carbon dioxide storage tank 2 and the carbon dioxide supply. Carbon dioxide transport pipe 7 connected via a pump 6
And the other end of the silicone oil transport pipe 5 is connected.
A spray nozzle 8 is provided at the insertion end of the extractor 3. Further, one end of a branch pipe 9 is connected to the carbon dioxide transport pipe 7, and the other end of the branch pipe 9 is inserted in the lower portion of the extractor 3.

While the silicone oil in the silicone oil storage tank 1 is being transported in the silicone oil transport pipe 5, the carbon dioxide in the supercritical or subcritical state in the carbon dioxide storage bath 2 is transferred to the carbon dioxide transport pipe 7. Is introduced into the silicone oil transport pipe 5 and mixed with the silicone oil, and the mixed fluid is jetted from the nozzle 8 to the upper portion in the extractor 3, while the supercritical or subcritical fluid in the carbon dioxide storage tank 2 is injected. Carbon dioxide in a critical state is introduced into the lower part of the extractor 3 through the branch pipe 9 and comes into countercurrent contact with the mixed fluid to extract impurities in the silicone oil.

Numeral 10 is an extract recovery tower, which is connected to the upper part of the extractor 3 by an extract recovery pipe 12 which is provided with an extraction phase heater 11, while 13 is a raffinate recovery tower, which is an extraction residue recovery tower. The extraction solvent (carbon dioxide), which is connected to the lower part of the extractor 3 by a raffinate recovery pipe 15 provided with a residual phase heater 14, and which extracts impurities (low molecular weight substances) in the extractor 3 is an extract. The carbon dioxide introduced into the extract recovery column 10 through the recovery pipe 12 and separated from the low molecular weight substance is returned to the carbon dioxide storage tank 2 through the carbon dioxide return pipe 17 provided with the cooler 16, and impurities are also contained. Is discharged from the extract discharge pipe 18. On the other hand, the silicone oil from which impurities (low-molecular-weight substances) have been extracted and removed in the extractor 3 is introduced into the raffinate recovery column 13 through the raffinate recovery pipe 15, and the silicone oil from which the accompanying carbon dioxide has been separated is separated. Is the residue discharge pipe 19
The carbon dioxide discharged further and separated from the silicone oil is returned to the carbon dioxide storage tank 2 through the return pipe 17.

[0033]

EXAMPLES The present invention will be described below in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] A high-molecular-weight, highly viscous dimethyl compound containing 0.3% by weight of a cyclic or acyclic organopolysiloxane low-boiling compound represented by the above general formula (2) or (3) as an impurity. Silicone oil (kinematic viscosity at room temperature 14000 cp) was used as an extraction raw material.

Using the apparatus shown in FIG. 1, a raw material of 800 g / h (containing low molecular weight impurities of 2.4 g / h) at 35 ° C.,
170 kg / cm ² G of carbon dioxide (1600 g / h) was mixed in the pipe, and this mixed fluid was heated at 40 ° C. and 150 kg / c.
A single nozzle having an inner diameter of 0.5 mm installed at the top of the column was supplied to an extracting device (inner diameter of the extracting section: 25 mm, height: 2970 mm) kept at m ² G. 800 from the bottom of the extraction tower
Carbon dioxide of g / h was separately supplied, carbon dioxide containing the extract was continuously discharged from the upper part of the extractor, and the raffinate was continuously discharged from the lower part of the extractor.

The extraction phase discharged from the upper part of the extractor is 1
It contained 5 g / h of extract, which contained 2 g / h of low molecular weight impurities. The raffinate discharged from the lower part of the extractor is 785 g / h of silicone oil,
Low molecular weight impurities were reduced to 0.4 g / h. In addition,
A Shimadzu GC-17A Capillary Gas Chromatograph and C-R6A Chromatopack were used to detect low molecular weight impurities.

[Example 2] The same raw material as in Example 1 was used.
0 g / h was used, which was mixed with carbon dioxide 1740 g / h at 35 ° C. and 170 kg / cm ² G in a pipe, and this mixed fluid was used in Example 1 which was kept at 40 ° C. and 150 kg / cm ² G It was supplied to the same extraction apparatus as above through a single nozzle having an inner diameter of 0.5 mm installed at the top of the column. Furthermore, 580 g / h of carbon dioxide is separately supplied from the lower part of the extraction tower,
Carbon dioxide containing the extract was continuously discharged from the upper part of the extractor, and the raffinate was continuously discharged from the lower part of the extractor.

The extraction phase contains 20 g / h of extract,
This contained 1.7 g / h of low molecular weight impurities. The extraction residue discharged from the lower part of the extraction tower is 560 g / h
No silicone was detected.

Comparative Example 1 The same raw material as used in Example 1 was used.
0 g / h was used, and the same extraction apparatus used in Example 1, which was maintained at 40 ° C. and 150 kg / cm ² G, was supplied from a tube having an inner diameter of 6 mm installed at the top of the column. 2400 g / h of carbon dioxide was supplied from the lower part of the extraction tower, carbon dioxide containing the extract was continuously discharged from the upper part of the extractor, and the raffinate was continuously discharged from the lower part of the extractor.

The extraction phase contains 10 g / h of extract,
This contained 1.0 g / h of low molecular weight impurities. The raffinate was 790 g / h of silicone oil and contained 1.4 g / h of impurities.

[0041]

According to the present invention, unnecessary unreacted low molecular weight substances and oligomer low molecular weight substances can be continuously and efficiently removed from silicone oil with high purity, and the silicone oil can be satisfactorily purified. it can.

[Brief description of the drawings]

FIG. 1 is a flow chart illustrating a preferred embodiment of the present invention.

[Explanation of symbols]

 1 Silicone Oil Storage Tank 2 Carbon Dioxide Storage Tank 3 Extractor 4 Supply Pump 5 Silicone Oil Transport Pipe 6 Supply Pump 7 Carbon Dioxide Transport Pipe 8 Nozzle 9 Branch Pipe 10 Extract Recovery Tower 11 Extraction Phase Heater 12 Extract Recovery Pipe 13 Extraction Residue Material recovery tower 14 Extraction residue heater 15 Extraction residue recovery pipe 16 Cooler 17 Carbon dioxide return pipe

Claims (3)

[Claims] [Claim 1] The following general formula (1) (In the formula, R ¹ and R ² are the same or different monovalent hydrocarbon groups or hydroxyl groups, R ³ and R ⁴ are the same or different monovalent hydrocarbon groups, and n is an integer of 100 to 3000. The silicone oil represented by the formula (1) is an extraction solvent in a supercritical state in which temperature and pressure exceed the critical value specific to the substance or in a subcritical state in which either temperature or pressure exceeds the critical value specific to the substance. The mixture is continuously contact-mixed, and then the mixed fluid is discharged and dispersed in an extractor pre-filled with an extraction solvent in a supercritical state or a subcritical state, and the extracted solvent is dispersed in the silicone oil of the above formula (1). A method for purifying a silicone oil, which comprises extracting and removing low molecular weight substances contained therein. 2. The method according to claim 1, wherein the mixed fluid is discharged and dispersed in a jet or spray state in the extractor. 3. The method according to claim 1, wherein the extraction solvent is carbon dioxide.