JPS618102A - Conductive microfilter - Google Patents

Abstract

PURPOSE:To prevent the danger of fire or electric shock caused by the generation of static electricity when a non-conductive substance such as oil is filtered, by using a conductive microfilter consisting of an olefin resin or a fluorocarbon resin and carbon black and having a specific range of apparent volume resistivity and an average pore size. CONSTITUTION:An olefin resin such as polyethylene or a fluorocarbon resin such as polychlorotrifluoroethylene, to which carbon black was added, is formed into a hollow yarn like membrane to form a microfilter. At this time, the amount to be added of carbon black is regulated so as to adjust apparent volume resistivity to 10<4>-10<-1>OMEGA.cm and an average pore size to 0.01-1mum. By this method, a conductive microfilter is obtained and the generation of static electricity by friction between the microfilter and a liquid at the time of filtering is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to membrane separation technology, and more particularly to a filter for precision filtration of non-conductive liquids such as oil.

[Conventional technology]

Conventionally, pre-coat filters have been generally used in oil purification processes, but recently it has become possible to efficiently purify oil by using microfilters made of hydrophobic resins. C% JP-A-55-79011, JP-A-58-93798, JP-A-58-17929
(Publication No. 7) [Problems to be solved by the invention] However, in the method using this microfilter,
During V over-operation when the outside air humidity is low, for example in winter, static electricity is generated due to friction between the microfilter and the oil.
In severe cases, it has become clear that sparks may be generated, posing a risk of fire or electric shock if workers come into contact with the product.

[Means for solving problems]

As a result of intensive study on the above problems, the present inventors found that
By using the conductive micro filter shown below, it is possible to mix the micro filter with non-conductive liquid such as oil.
There is no generation of static electricity due to lK, and as a result, there is no risk of fire or electric shock, and it has become possible to efficiently and precisely purify non-conductive liquids such as oil.

That is, the present invention is made of an olefin resin or a fluororesin and carbon black, has an apparent volume resistivity of 104 to 10-''Ω·m, and has an average pore diameter of 0.01 to 1 μm.
It is a conductive micro filter.

The resin used in the present invention needs to be an olefin resin or a fluororesin. Specifically, polyolefins such as polyethylene, polypropylene, polybutene, and poly-4-methylpentene-1; halides of these polyolefins containing one or more fluorine atoms, 4-fluorinated ethylene-perfluoroalkyl vinyl ether copolymers, and , ethylene, propylene, butene, isobutylene, pentene, hexane, 1-7-fluorinated ethylene, vinylidene fluoride, 3-fluorinated ethylene, 4-fluorinated ethylene, 3-fluorinated chloroethylene, 6-fluorinated propylene Copolymers consisting of a combination of ethylene hydrocarbons such as ethylene hydrocarbons or rhodane-substituted ethylene hydrocarbons containing one or more fluorine atoms, and blend polymers of these polymers are used.

The carbon black used in the present invention is necessary in order to impart electrical conductivity to the microfilter and to reduce generation of static electricity due to friction between the microfilter and the liquid. Various conductive fine powders such as metal powders can be considered as additives for imparting conductivity, but since the particle size is small and has good affinity with hydrophobic resins (olefin resins or fluorine resins), they can be applied uniformly to the resin. Carbon black is preferred because it can be dispersed throughout the filter to provide a microfilter with a uniform pore size distribution and high conductivity.

The microfilter of the present invention substantially eliminates static electricity generation due to friction between the microfilter and liquid during filtration.
It also provides sufficient strength as a filter. Therefore, it is necessary to adjust the amount of carbon black added to make the apparent volume resistivity 104 to 10-10 m2.

If it exceeds io', there is virtually no antistatic effect;
If it is less than io-', it is necessary to add a very large amount of carbon black, and as a result, the strength of the filter decreases and it becomes easy to break during use, which is not preferable. The average pore diameter is 0.
01-1μ is preferable. If it is less than 0.01μ, the amount of permeation will be small and the filtration effect will be poor, and if it exceeds 1μ, removal of foreign matter will not be sufficient, and both are not preferred as microfilters. In addition, the shape of the micro 2 filter can be pleated, flat membrane, tube, or hollow fiber.
A hollow fiber shape is preferable for reasons such as compactness of the device when modularized and simplification of the structure.

Hereinafter, the present invention will be specifically explained with reference to Examples.

The physical properties shown in the examples of the present invention were determined by the following measurement method.

Constructed volume resistivity〉 It is a volume resistivity that includes pores, and New Experimental Chemistry Course 19
Polymer Chemistry I [edited by the Chemical Society of Japan (1978), p. 943
Performed according to the four-probe method shown in .

average pore diameter〉 By mercury porosimeter.

Porosity Porosity = (pore volume/membrane volume) X Zo.

Pore volume = Water content weight - Absolute dry weight - Stagnation voltage> Based on a static electricity meter (trade name: Statylon M ■ manufactured by Anato Shokai).

Examples 1 to 3 and Comparative Examples 1 to 3 A rapeseed oil p-permeability test was conducted using the A-F membrane shown below as a microfilter.

A membrane: High-density polyethylene (product name: Santic S-
After kneading 23.0% by weight of 360P), 53.5 fit% of di-(2-ethylhexyl)7 thale, and 23.5% by weight of finely divided silica, the mixture was melt-extruded using a twin-screw extruder and a hollow nozzle. -(2-Ethylhexyl) phthalate and finely divided silica were removed to obtain a hollow fiber porous membrane made of high-density polyethylene.

This membrane had an average pore diameter of 0.12 μm, a porosity of 7°, and an apparent volume resistivity of 15Ω.

B membrane: polychlorotrifluoroethylene (trade name: Daiflon M-300) 32.3% by weight, chlorotrifluoroethylene oligomer (trade name: Daiflo Luna 20) 33.9% by weight,
tri(2-ethylhexyl)trimerite) '17
．． After mixing 0% by weight and 16.8% by weight of fine powder silica, a hollow thread-like porous membrane made of polychlorotrifluoroethylene was obtained in the same manner as membrane A. This membrane has an average pore size of 0.11μ
, porosity 72%, apparent volume resistivity) 1015Ω・
He was a deputy.

C membrane: Polychlorotrifluoroethylene (trade name: Daiflon M-300) 32.4% by weight, chlorotrifluoroethylene oligomer (trade name: Daifloil ÷20)
) 16.0% by weight, tri(2-ethylhexyl)
After kneading 16.0% by weight of trimellitate, 15.8% by weight of finely divided silica, and 3.8% by weight of carbon black (trade name: Ketjenblack EC), the mixture was melt-extruded using a twin-screw extruder and a hollow nozzle, and then chloro Trifluoroethylene oligomer, tri(2-ethylhexyl) trimellitate, and finely divided silica were removed to obtain a hollow fiber porous membrane made of polychlorotrifluoroethylene and carbon black. This membrane has an average pore diameter of 0.09μ, a porosity of 68μ, and an apparent volume resistivity of 1.
It was 5×10'Ω·α.

D membrane: High-density polyethylene (product name: Santic S-
After kneading 25.2% by weight of 360P, 57.8% by weight of diisodecyl phthalate and 17.1% by weight of carbon black (trade name: Ketjenblack EC), the mixture was melt-extruded using a twin-screw extruder and a hollow nozzle. Thereafter, the 7-talate was removed using DiIndage J to obtain a hollow fiber-like porous membrane consisting of high-density polyethylene and carbon black. This membrane has an average pore diameter of 0.30μ, a porosity of 60μ, and an apparent volume resistivity of 1. I x 10°Ω・sub.

E membrane: 34.5% by weight of polychlorotrifluoroethylene (product name: Dia 0 Iruna 20), chlorotrifluoroethylene oligomer (product name: Dia 0 Iruna 20)
) 36.6% by weight, tri(2-ethylhexyl)
After mixing 18.2% by weight of trimellitate and 10.6% by weight of carbon black (trade name: Ketjenblack EC), a porous film made of polychlorotrifluoroethylene and carbon black was obtained in the same manner as film D. This membrane is
The average pore diameter was 0.05 μm, the porosity was 46%, and the apparent volume resistivity was 3.2×10°Ω·m.

F membrane: 26.4% by weight of ethylene-tetrafluoroethylene copolymer (trade name: Aflon COP), 51.6% by weight of chlorotrifluoroethylene oligomer (trade name: Daifloil ÷20), silicone oil (trade name: K
F-96) s, s wt%, fine powder silica 11.3 wt%
, carbon black (product name: Ketjen Black EC
) After mixing 2.2% by weight, a hollow fiber porous membrane made of ethylene-tetrafluoroethylene copolymer and Carpump Vic was obtained in the same manner as the C membrane. This membrane has an average pore size of 0
．． 17μ, porosity 60%, apparent volume resistivity 4.7
X 10”Ω・Vice.

The microfilters made of the six types of membranes described above were each incorporated into the module shown in FIG. In Figure 1, 1
is a microfilter, 2 is an adhesive made of conductive epoxy resin to which 15% by weight of carbon black has been added, and 3 is a housing made of conductive polypropylene to which 15% by weight of carbon black has been added. 4 is ground. Using these modules, moisture content is reduced to 1.2 in winter (room temperature 2°C, humidity 30%).
-% by weight of rapeseed oil was filtered with lacrimal overpressure IK9/-. The results of 7 are shown in Table 1.

Blank space below [Effects of the invention] According to the present invention, moisture, gum, and wax content in non-conductive liquids having a specific conductivity of lo-70·on''-1 or less, such as vegetable oils, animal oils, mineral oils, and organic solvents, can be improved. Precise purification is also possible without the risk of fire or electric shock due to static electricity generated during filtration.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of the module used in Examples and Comparative Examples. In the figure; 1 is a microfilter, 2 is a conductive resin, 3 is a housing made of conductive polypropylene, and 4 is a ground.

Claims (1)

[Claims] It is made of olefin resin or fluororesin and carbon black, and has an apparent volume resistivity of 10^4 to 10^-
^1Ω・cm, conductive microfilter with average pore size of 0.01 to 1μ