JPH0454716B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for recycling waste fluorine-based synthetic lubricating oil, and more specifically, to easily regenerate waste oil of fluorine-based synthetic lubricating oil to the same quality as new oil. It is about the method. (Technical background) Fluorine-based synthetic lubricating oil

It is a synthetic lubricating oil with the general formula of [Formula] or CF ₃ - (O-CF ₂ ) _x - O-CF ₃ , and has better oxidation resistance and chemical resistance than other lubricating oils. sex,
It is known as a non-toxic lubricating oil with excellent heat resistance. Also, its physical properties are significantly different from other lubricating oils. For example, it has physical properties such as having a higher specific gravity than other lubricating oils, being insoluble in water and almost all organic solvents, and being extremely chemically stable. As described above, fluorine-based synthetic lubricating oils have excellent properties that other lubricating oils do not have, and due to their physical properties, they are mainly used in fields where heat resistance and oxidation resistance are required, or where stable lubrication performance over a long period of time is required. It is often used in fields where Furthermore, in recent years, fluorine-based synthetic lubricating oils have attracted attention as vacuum technology materials due to their properties, and have come to be widely used, especially as lubricating oils for vacuum pumps used in the electronic industry. this is,
Fluorine-based synthetic lubricants are superior in terms of the properties required for lubricants used in vacuum pumps: lubricity, oxidation resistance, heat resistance, chemical resistance, low vapor pressure, radiation resistance, and non-toxicity. It has been recognized that it is extremely superior to other lubricants, and is particularly chemically stable, making it suitable for use in the electronics industry, which often uses highly corrosive, dusty, and dangerous gases. It has come to be widely used as a lubricant for vacuum pumps. However, even if the lubricating oil used in this vacuum pump is a chemically very stable fluorine-based synthetic lubricating oil, various substances discharged from the system that should be evacuated may be mixed in or particles from the vacuum pump may be contaminated. Contamination, etc.
Furthermore, if the fluorine-based synthetic lubricating oil itself becomes contaminated and deteriorates, it will eventually be disposed of. Fluorine-based synthetic lubricants are chemically inert and therefore less susceptible to deterioration than petroleum-based lubricants, making them advantageous as lubricants for vacuum pumps. However, on the other hand, they are susceptible to contamination. Impurities are never dissolved. As a result, contaminants accumulate in the lubricating oil. Therefore, when using waste fluorine-based synthetic lubricating oil, impurities are present in suspension in the lubricating oil, so the new lubricating oil, which was colorless and transparent in its viscosity, gradually becomes opaque as it is used. Eventually, it becomes waste oil with a blackish-brown viscosity. In general, the standard for replacing lubricating oil used in vacuum pumps used in dry etching processes in the electronics industry, particularly in semiconductor device manufacturing, is determined by the pumping speed of the vacuum pump. When the exhaust speed decreases, impurities generated by etching become difficult to exhaust and remain in the etching chamber, adversely affecting the etching process of the object to be etched, resulting in variations in etching. For example, in an etching process using a mixed gas of CF ₄ and O ₂ , after activating the vacuum pump,
If it takes 13 seconds or more to reach 0.2Torr, which used to take 9-10 seconds with new oil, you will start to see variations in etching. At this time, the lubricating oil has become blackish brown and opaque. Using such lubricants for a long period of time not only has a negative effect on the etching process, but also
When the vacuum pump is operated, impurities in the lubricating oil reduce the lubricity and have a negative effect on the pump parts (especially the bearings and seals on the rotating shaft), significantly impairing the functionality of the vacuum pump and, as a result, causing the desired Lubricating oil that has turned blackish brown cannot be used because it takes a long time to reach the vacuum level and also lowers the ultimate pressure of the vacuum pump, so it becomes waste oil. As is well known, fluorine-based synthetic lubricating oil is chemically very stable and nonflammable, so waste oil cannot be incinerated or thermally decomposed. The disposal of waste oil has become a major problem. Fluorine-based synthetic lubricating oils are very expensive compared to other synthetic lubricating oils, and there has been a strong desire to develop a method for recycling waste oil, especially in the electronics industry, where lubricating oils are often replaced. (Purpose of the Invention) The present invention was made as a result of intensive research in view of such demands, and its purpose is to obtain recycled oil from which impurities in waste oil of fluorine-based synthetic lubricating oil have been completely removed. . (Structure of the Invention) The present invention involves adding and mixing a fluorinated solvent to waste oil of fluorinated synthetic lubricating oil, causing some of the impurities to float to the upper layer of the resulting mixed solution, and then removing the impurities. Further, a non-fluorinated solvent is added to the mixed solution and stirred to separate into two layers, and the remaining impurities are transferred to the upper layer of non-fluorinated solvent, and then the fluorinated solvent and the fluorinated synthetic lubricant are mixed. After separating the oil-containing lower layer, the fluorinated synthetic lubricating oil is left by volatilizing the fluorinated solvent and the trace amount of non-fluorinated solvent from the separated layer. This is a method for recycling waste oil of fluorine-based synthetic lubricating oil, which is characterized by: Further, when carrying out the present invention, a fluorine-based solvent and a non-fluorine-based solvent can be used simultaneously. Furthermore, in the present invention, it is preferable to remove solid impurities at any stage. As means for removing solid impurities, conventional means for separating solids and liquids can be used. The details of the configuration of the present invention will be explained in detail below. (Waste oil of fluorine-based synthetic lubricating oil) The waste oil used in the present invention may be any fluorine-based synthetic lubricating oil, for example, in fields where properties such as heat resistance and oxidation resistance stability are particularly required. It is waste oil of fluorine-based synthetic lubricating oil of polymers and oligomers such as perfluoropolyether, perfluoropolyphenyl ether, or perfluoropolyether triazine used in vacuum pumps (for example, vacuum pumps, etc.). (Fluorine-based solvent) As the fluorine-based solvent, any solvent that can be dissolved in the fluorine-based synthetic lubricating oil and phase may be used. For example, trichloromonofluoromethane, tetrachlorodifluoroethane,
Trichlorotrifluorothane, azeotrope of trichlorotrifluoroethane and methylene chloride,
Examples include an azeotrope of trichlorotrifluoroethane and ethyl alcohol, a mixture of trichlorotrifluoroethane and isopropyl alcohol, and dibromotetrafluoroethane. (Non-fluorine solvent) In the present invention, water and a non-fluorine organic solvent are collectively referred to as a non-fluorine solvent. Any fluorine-free organic solvent may be used as long as it can extract impurities from waste oil. Examples of such substances include pentane, hexane, heptane,
Hydrocarbons such as octane, ligroin, kerosene, naphtha, cyclohexane, toluene, xylene,
Halogenated hydrocarbons such as methylene chloride, carbon tetrachloride, ethylene chloride, trichloroethane, hexyl chloride, alcohols such as methanol, ethanol, n-propanol, isopropanol, butanol, amyl alcohol, hexanol, heptanol, isopropyl ether, butyl ether, Ethers such as furfural, ketones such as acetone, methylacetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, diisobutyl ketone, acetonylacetone, diacetone alcohol, isophorone, methyl acetate, ethyl acetate, butyl acetate, etc. Polyhydric alcohols and their derivatives such as esters of , ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, and ethylene glycol monoethyl ether acetate can be used. (Regeneration Method) The first step in the method for regenerating waste oil of fluorine-based synthetic lubricating oil of the present invention is to mix and dissolve the waste oil and the fluorine-based solvent. Fluorine-based synthetic lubricating oils have the property of being insoluble in water and most organic solvents, but are known to be soluble in fluorine-based solvents. Furthermore, fluorine-based solvents have high selective solubility, are chemically stable solvents, have extremely low surface tension, and have high specific gravity. The waste oil and this fluorine-based solvent are mutually mixed to reduce the viscosity of the waste oil and form a mixed solution with a high specific gravity. By doing so, some of the impurities in the waste oil easily float to the upper layer of the mixed solution and are separated, and the lower layer of the mixed solution becomes a colorless and transparent solution. The mixing ratio of waste oil and fluorine-based solvent may be at least 1 part by weight of fluorine-based solvent per 1 part by weight of waste oil.
If the amount of solvent is too large, the subsequent solvent removal process will take time, so it is usually preferable to use 1 to 10 parts by weight of the fluorinated solvent per 1 part by weight of waste oil. If the fluorine-based synthetic lubricating oil is extremely contaminated, it is effective to remove some impurities in the waste oil by centrifuging the waste oil before adding the fluorine-based solvent, and then add the fluorine-based solvent. . In addition, by simply adding a fluorine-based solvent to waste oil, mixing it, and allowing it to stand, impurities in the waste oil will separate into the upper layer, and a colorless and transparent viscous solution will appear in the lower layer immediately (after about 30 minutes). However, in this case as well, impurities may be actively separated using a centrifuge or the like. The second step of the invention consists of removing impurities that could not be removed in the first step. That is, by adding a fluorine-free organic solvent and, if necessary, water to the lower layer solution obtained in the first step and stirring vigorously, impurities are extracted into the fluorine-free solvent layer. Next, collect the lower layer solution by standing or centrifuging. Further, the first step and the second step of the present invention
It is also possible to perform these steps at the same time. That is, a fluorine-containing solvent, a non-fluorine-containing organic solvent, and, if necessary, water are added to the waste oil and stirred to form an upper layer containing impurities, which is then removed. The adoption or rejection of this operation must be determined depending on the contamination status of the waste oil, but it is recommended to perform the first and second steps simultaneously to determine whether impurities have been extracted sufficiently. You can make decisions quickly and easily. The third step of the present invention is to obtain a regenerated fluorine-based synthetic lubricating oil by removing substances other than the fluorine-based synthetic lubricating oil from the lower layer solution obtained in the second step. Consists of. Removal of fluorine-based insolvents, non-fluorine-based organic solvents, and water from mixed solutions does not require a particularly limited method to obtain good results; ordinary volatilization treatment or distillation treatment can be used. It can be easily removed by doing the following. Also, after these treatments,
Further, a vacuum distillation treatment may be performed to more completely remove the solvent. At this time, some fluorine atoms may be dissociated from the fluorine-based synthetic lubricating oil, but this is because fluorine atoms are added by introducing fluorine gas and making contact, and the original state is restored. Can be done. When solids such as metal powders are mixed in the waste oil of fluorine-based synthetic lubricating oil, it is desirable to remove the solids by conventional means such as filtration at any stage of the regeneration process. Preferably, it is easier when a fluorine-based solvent is mixed because the viscosity is low. The recycled fluorine-based synthetic lubricating oil obtained as described above is completely colorless and transparent in appearance and has viscosity, and has properties and performance that are the same as new oil. Next, an example of the operation for carrying out the method of the present invention will be described with reference to the attached FIG. 1. A fluorine-based solvent 3 is added to a first mixing tank 2 containing waste oil 1 of fluorine-based synthetic lubricating oil. After the addition of the fluorine-based solvent 3 is completed, the contents of the first mixing tank 2 are thoroughly stirred. Then, the waste oil of the fluorinated synthetic lubricating oil and the fluorinated solvent will uniformly mix to form a solution, so when the contents of the first mixing tank are left still, some of the impurities will float to the top of the solution. As a result, two layers are formed in the first mixing tank. Therefore, the upper layer and the lower layer are separated by a suitable means such as decantation, the upper layer is discarded, and the lower layer 4 is transferred to the second mixing tank 5. Next, a fluorine-free solvent 6 is added to the second mixing tank 5, and the contents of the second mixing tank are stirred. Then, the impurities remaining in the lower layer 4 formed in the first mixing tank migrate into the non-fluorine solvent. Thereafter, when the contents of the second mixing tank are allowed to stand still, the non-fluorinated solvent floats to form an upper layer. Then, the upper layer and the lower layer are separated by a suitable means such as decantation. This upper layer contains impurities, so it should be discarded or
Alternatively, it is subjected to a purification treatment to recover non-fluorinated solvents. The lower layer 7 formed in the second mixing tank is transferred to the evaporator 8
Move to. This lower layer 7 contains a fluorine-based solvent and a small amount of non-fluorine-based solvent, so if an appropriate evaporation method such as reduced pressure heating is applied to the evaporator, the fluorine-based solvent and the non-fluorine-based solvent are evaporated. The regenerated fluorinated lubricating oil remains in the evaporator. (Example) The present invention will be described in detail with reference to Examples below. Example 1 In the dry etching processing equipment, when using new oil, the vacuum pump could be evacuated to 0.2 Torr in about 9 seconds after starting the vacuum pump, but now it takes about 13 seconds, and there are also variations in etching. Pour 500 g of waste oil (blackish brown) from a vacuum pump that used the fluorinated synthetic lubricating oil Fomblin (trade name, manufactured by Montegisson) into the separatory funnel in step 2, and add Diflon Solvent, a fluorinated solvent, to it. Add 1 kg of S-3 (trade name, trichlorofluoroethane manufactured by Daikin Industries, Ltd.),
After vigorously stirring and mixing for a minute, the mixture was allowed to stand for 10 minutes. After standing still, impurities in the waste oil were separated in the upper layer as a blackish brown color, and a solution containing a mixture of Fomblin and Daiflon Solvent S-3 was separated in the lower layer.
Next, the lower layer solution was collected, filtered through paper, and transferred to beaker No. 5. One portion of water and one portion of acetone were added, and the mixture was vigorously stirred and mixed for 5 minutes, and then allowed to stand for 30 minutes. Next, collect the lower layer solution, transfer it to the distillation flask in step 1, put this beaker in a hot bath, keep the temperature at 70℃~80℃, and completely remove Daiflon Solvent S-3, acetone and water under reduced pressure. Distilled off to obtain regenerated Fonbri. Example In the dry etching processing equipment, when using new oil, the vacuum pump could be evacuated to 0.2 Torr in about 10 seconds after starting the vacuum pump, but now it takes about 15 seconds, and there are also variations in etching. Varielta, a fluorine-based synthetic lubricant
J100 (Product name, manufactured by Japan Oil Seal Industry Co., Ltd.)
Put 500 g of waste oil (blackish brown) from a vacuum pump using
Co., Ltd.) and stirred vigorously for 1 minute.
It was left to stand for 10 minutes. After standing still, impurities in the waste oil appear blackish brown and separate in the upper layer, and varielta appears in the lower layer.
A mixed solution of J100 and Magic Dry E-6 was separated. Next, collect the lower layer solution and put it in a beaker of 5. Water 1.5 and methanol 1.5
After stirring and mixing vigorously for 5 minutes, the mixture was allowed to stand for 10 minutes. Next, collect the lower layer, put it in flask 2, and use the usual distillation method to completely remove the remaining Magic Dry E-6, methanol, and water.
Got a recycled Barrierta J100 that was on paper.
When we similarly measured the time to reach 0.2 Torr using this regenerated Varierta J100, we found that it had the same pumping speed as the new oil, and there was no variation in etching. (Effects of the Invention) The method for recycling waste fluorine-based synthetic lubricating oil according to the present invention can quickly obtain recycled oil with a high yield through simple operations, and has the same properties and performance as new oil. This makes it possible to use fluorine-based synthetic lubricants, which are extremely expensive and highly practical, over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a flowchart illustrating an example of a procedure for carrying out the method of the present invention. Reference symbols in the drawings have the following meanings. 1... Waste oil of fluorine-based synthetic lubricating oil, 2... 1st
Mixing tank, 3...Fluorinated solvent, 4...Lower layer of first mixed liquid, 5...Second mixing tank, 6...Non-fluorinated solvent, 7...Lower layer of second mixed liquid, 8... ...evaporator, 9
...Fluorinated solvent vapor and non-fluorinated solvent vapor.

Claims (1)

[Claims] 1. A fluorinated solvent is added to waste fluorinated synthetic lubricating oil and mixed, some of the impurities are floated to the upper layer of the resulting mixed solution, and the impurities are removed and then mixed. A non-fluorinated solvent is further added to the solution and stirred to separate into two layers, and the remaining impurities are transferred into the upper layer of non-fluorinated solvent, which then contains a fluorinated solvent and a fluorinated synthetic lubricating oil. A fluorine-based synthetic lubricating oil is left behind by evaporating the fluorine-based solvent and a trace amount of non-fluorine-based solvent from the fractionated layer after separating the lower layer. A method for recycling waste oil from synthetic lubricants. 2. The method according to claim 1, wherein the solution is a mixture of waste oil of fluorine-based synthetic lubricating oil and a fluorine-based solvent from which solid impurities have been removed. 3. The method according to claim 1 or 2, which uses two or more fluorine-free solvents. 4. The method according to claim 3, wherein one of the non-fluorinated solvents is water. 5. The method according to any one of claims 1 to 4, wherein a fluorine-based solvent is added to a fluorine-free solvent.