JPH0651088B2 - Regeneration method of lubricating oil for vacuum pump - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for regenerating a lubricating oil for a vacuum pump.

[Conventional technology]

Vacuum pumps, especially those used in semiconductor manufacturing equipment, are mixed with a large amount of corrosive gas and are accompanied by reaction products of various gases, some of which are processed by an exhaust system but mixed with vacuum pump oil. Pollutes oil. Therefore, these impurities (acid,
It is necessary to remove oxidation products, metal powder, dust, etc.) by filtration. There are various conventional techniques for this.

1. Filter method (cellulose, glass fiber, sintered material, etc.) 2. Adsorbent filter method (activated alumina filter, activated clay filter, etc.) 3. Electrostatic filtration method 4. Combination method 5. Extraction separation method (in oil) Contaminants are extracted into water by adding water or an aqueous solution and separated by the difference in specific gravity.) 1. Filter method This method has a pleated filter and a roll tissue type filter, and removes contaminants on the surface of the filter material.
This type of filter removes only solid contaminants, the filtration accuracy is relatively low, and there is a lot of oil loss when the filter is replaced.

As this filter system, the filters disclosed in JP-A-56-7609 and JP-A-62-24904 are known. The former filter uses a fiber assembly containing a water-swellable fiber in which a part of the outer layer part is a hydrophilic cross-linked polymer and the rest is a polymer such as an acrylonitrile polymer, and the latter filter is hydrophilic. It is composed of a long-fiber highly water-absorbent material such as an acrylic or cellulose-based material substituted with a functional group. However, even though these filters can remove water in the oil, they cannot remove acidic components in the oil and thus cannot be used for complete regeneration of the lubricating oil of the vacuum pump. .

2. Adsorbent filter method This is a filter that mainly uses activated alumina, and if the powder is made fine to improve the filtration performance, clogging is likely to occur. Since the adsorption amount of acid is determined by the filling amount, it becomes large when the adsorption amount is increased. The filter is expensive and there is a lot of oil loss when changing the filter.

3. Electrostatic filtration method This is a device for collecting static electricity between the opposite electrode plates, and the device for generating static electricity becomes large. Conditions under which an electric current easily flows, that is, oil with a high acid value, oil mixed with water, highly contaminated oil, etc. cannot be used. There is no acid removal function. Furthermore, the amount of oil used is large,
The filtration rate is slow.

4. Combination method A Pleated filter and activated alumina filter Pleated filter is used to remove large contaminants, and activated alumina filter is used to remove small contaminants and acid adsorption.

The amount of oil used is extremely high when replacing the filter. It becomes larger and more expensive.

B Electrostatic Filtration and Activated Alumina Adsorption Filter Due to space restrictions, the amount of activated alumina filled is small, the amount of acid treated is small, and the loss of oil is large and the cost is high.

5. Extraction separation method Add an aqueous solution to the oil to extract contaminants and separate them by specific gravity.

It is effective for water-soluble contaminants, but filtration accuracy is poor when various contaminants coexist.

[Problems to be Solved by the Invention]

As described above, all of the conventional methods have a problem with respect to the regeneration of the lubricating oil of the vacuum pump, and in particular, they are insufficient methods for removing the acidic component that adversely affects the lubricating oil.

The present invention has been made in consideration of the above circumstances, and provides a regeneration method capable of efficiently removing an acidic component during regeneration of a lubricating oil of a vacuum pump and enabling its long-term cyclic use. To aim.

[Means and Actions for Solving the Problems]

In the regeneration method of the present invention, the lubricating oil in the vacuum pump is circulated and supplied to the filtration element containing the acrylic water-absorbent fiber which is hydrated in the water content range of 0.1 to 30% to obtain the acidic component in the lubricating oil. Is removed.

The filtration element including the water-containing acrylic water-absorbent fiber has a moisture layer on the surface of the constituent fibers, and the moisture layer on this surface acts to remove the acidic components mixed in the lubricating oil of the vacuum pump. . That is, the water layer formed on the surface layer of the fiber by hydration activates the acid substituents present inside the fiber and has a function of strongly capturing the acidic substance in contact with the water layer, whereby the initial acid This is to increase the sum efficiency. Therefore, by circulatingly supplying the lubricating oil in the vacuum pump to the filter element, the acidic components in the lubricating oil are gradually removed, and the final regeneration of the lubricating oil can be efficiently performed.

The range of the water content having the acidic component removing function is 0.1 to 30%, preferably 3 to 15%.
When the water content is 0.1% or less, the acidic component removing function is not sufficient, and when the water content is 30% or more, the fiber elasticity of the acrylic fiber is lost and the shape of the filtration element cannot be maintained.

〔Example〕

Examples and drawings illustrating the present invention will be described.

The figure shows an example in which the method of the present invention is applied to a closed circulation type filtration device. The vacuum pump 10 has an intake port 12 and an exhaust port 14, and connects the intake port 12 to a required device. The lubricating oil circuit forms a circuit 32 connecting from the drain port 16 to the oil supply port 18 via the pump 20 and the filtering device 22. Oil is introduced into the filter tank 24 of the filtering device 22 from the bottom inlet 26, the oil rises, passes through the annular filter element 28, and returns from the bottom outlet 30 to the oil supply port 18.

An example of an implementation of the filter element 28 suitable for the above construction is as follows.

Shape, outer diameter 180mm, height 115mm, donut type Fiber filling rate 5-50% Fiber moisture content 0.1-30% Fiber type Acrylic water-absorbent fiber Other fiber, non-woven fabric, cotton element, wound element, etc. And get it.

Pump Pressurized oil circulation pump (0.1-15 lt / min) Although the configuration shown is a continuous circulation closed filtration device directly connected to a vacuum pump, it forms a bypass in the circuit or supplies oil from the tank of the vacuum pump. It goes without saying that the filtering device can also recycle the used lubricating oil in this tank or another tank.

An example of implementation of the illustrated filtration device of the present invention will be shown below as an example of regeneration of vacuum pump oil in a chlorine-based dry etching process.

Regeneration treatment condition Oil Fluorine-based synthetic oil (BARRIERTA J25) Treatment oil amount 10 lt Circulation pump flow rate 1.3 lt / min Filter tank capacity 3.5 lt Treatment temperature Normal temperature element 180 φ X 115mm Fiber filling rate 20% Fiber moisture content 10% Analysis result treatment Previous analysis value Weight pollution degree 106 mg / 100 ml Strong acid value 150 mg / l Analysis value after treatment Treatment time hr 0 1 2 3 Weight pollution degree mg / 100 ml 106 13 1.2 0 Strong acid value mg / l 105 22 1.8 0 Fluorine-based Table 1 below shows an example of continuous use in the dry etching step, which is used under the same conditions as other known filtration methods.

Usage conditions Oil used Matsumura Oil Research Institute MR-200 Viscosity 73.6 cst / 40 ° Total acid value 0 Weight pollution degree 0 Vacuum pump Japan Vacuum Giken D-950 Working atmosphere gas Freon Compared with conventional treatment methods, viscosity and total acid It has become possible to maintain and control the price and pollution level over a long period of time.

Table 2 shows that a fluorine-based synthetic oil 10 is used as a lubricating oil for a vacuum pump (D-950, manufactured by Nippon Vacuum Technology Co., Ltd.). The results are shown in the case of circulating supply. It can be seen from the table that the water content of 0.1 to 30%, preferably 3 to 15%, is sufficient to remove acidic components.

[Effects of the Invention] 1. Removal of Acid The acrylic water-absorbent fiber filter element according to the present invention contains 0.1-30% of water so that the acid in the oil is replaced by water to control the increase in oxidation. Produces a sum effect. Therefore, by circulating and supplying the lubricating oil of the vacuum pump, the acidic component can be reliably removed.

2. Removal of contaminants and reaction products Contaminants adhere to the fiber surface and are sequentially deposited to remove contaminants by processing.

3. Removal when acid and contaminants coexist The contaminants adhere to the fiber surface, and the acid is replaced by the water layer and removed.

4. Adaptability to usage conditions The filter element of the present invention is easy to adjust density, moisture content, and be processed into various shapes, and can be easily adapted to various usage conditions.

That is, the density is set low when a large amount of contaminant products is mixed. Increase the water content if there is a large amount of acid. This operation can be easily performed when adjusting and filling the filter element.

In addition, the water-containing acrylic water-absorbent fiber of the present invention has a strong adsorption power because the surface of the fiber is activated by the water content. Therefore, even if the fiber density is rough,
Can remove acids, contaminants and other harmful substances,
It can be used for a long time without long clogging. Then, by removing these harmful substances, it is possible to surely regenerate the lubricating oil of the vacuum pump.

By using the filtration device of the present invention, the used oil of the vacuum pump can be regenerated to the required standard, which is remarkably effective in semiconductor manufacturing.

[Brief description of drawings]

The figure is a diagram showing an example of a method for regenerating a vacuum pump lubricating oil according to the present invention. 10 ... Vacuum pump 12 ... Intake port 14 ... Exhaust port 16 ... Drain port 18 ... Oil supply port 20 ... Circulation pump 22 ... Filtration device 24 ... Filter tank 28 ... Filter element

Claims (1)

[Claims] 1. A lubricating oil in a vacuum pump is circulated and supplied to a filter element containing an acrylic water-absorbent fiber which has a water content of 0.1 to 30% to remove an acidic component in the lubricating oil. A method for regenerating a lubricating oil for a vacuum pump, comprising: