JPH01199618A - Filter for filtration - Google Patents

Abstract

PURPOSE:To obtain a filter very stable even under high pressure and having high water permeability and satisfactory filtering efficiency by adding glass frit to zinc oxide whiskers having a specified structure and by calcining them. CONSTITUTION:Glass frit is added to zinc oxide whiskers each branched in two or more directions and they are calcined. The acicular parts of the whiskers intercross and an extremely superior filtering structure having high porosity is formed. The deterioration of the filtering characteristics under high pressure is improved and a filter for filtration having a high rate of rejection and high permeability under high pressure as well as under ordinary pressure is obtd. The filter may be a water treating filter or an air purifying filter.

Description

[Detailed description of the invention] Industrial applications The present invention is a water treatment filter for dirt treatment, water supply, etc.

It relates to filtration filters that are used as air purification filters, suspension processing filters in the food industry, etc., water and wastewater process filters in the chemical industry, etc.

Conventional technology Conventional filtration filters include ■organic materials such as F paper and P cloth.
, those that are connected by entangling them, those that are connected using a different type of binder like non-woven fabric, ■ Wire mesh.

Fine wire materials such as glass mats and glass cloth, inorganic fibers entwined with each other or connected with a binder, organic sheet materials with 6 micropores, and inorganic materials such as cD sintered metals. There are also those in which non-fibrous particulates are welded or connected with a different type of binder.

Problems to be Solved by the Invention Each of these has its own features, but in terms of filtration efficiency, ■＠ has good rejection and permeability under low pressure if the diameter of the fibrous material is small, but it has good rejection and permeability under high pressure. In this case, the fibers become compacted due to deformation and the permeability decreases. @ has a limited pore formation density even under low pressure and is inferior to the former in permeability. Also, under high pressure, the pore size changes due to compaction and the transmittance decreases. ■ is under low pressure.

Although the pore size does not change under high pressure, the porosity does not increase sufficiently.

The present invention improves the problem of conventional various filters, which is the decline in filtration characteristics under high pressure, and improves the filtration characteristics under normal pressure.

The purpose of this invention is to provide a filter that achieves high rejection rate and high permeability under high pressure.

Means for Solving the Problems The present invention is made by adding glass frit to zinc oxide whiskers having a structure branched in two or more directions and firing the resulting whiskers.

Function: The acicular portions of the whiskers are intertwined with each other, achieving an extremely excellent F material structure with fine pores and high porosity. The pore size is reduced by the press pressure during molding, and the intersections of the needle-shaped parts are connected by melting the added glass frit. In addition, the above whiskers have good wetting properties with water, solvents, etc., and are a single crystal material with a strength close to that of a perfect crystal with no internal lattice defects, and exhibit filtration properties without changing at all even under high pressure. It is something to do.

Example One embodiment of the present invention will be described below.

First, zinc oxide whiskers produced by oxidizing metallic zinc are prepared. Specifically, this zinc oxide whisker is different from conventional zinc oxide manufacturing methods and zinc oxide whisker manufacturing methods.

Obtained by using metallic zinc powder.

Particle diameters of 0.1 to 500 μm can be used, and among them, those of 10 to 300 μm give the best results. Preferably, these metallic zinc powders are powders obtained by spraying zinc wire or zinc powder into the air using an arc-type thermal spraying device, but other pulverization methods may also be used.

Zinc powder within the above range obtained by a spray method, a stamp mill method, or a ball mill method can also be used.

As a method for forming an oxide film on the surface of the above zinc powder, the following method is preferable. First, mechanical treatment in the coexistence of water is performed using a mortar-type thinning machine, a roll, etc., and mechanical pressure is applied to each particle.

Furthermore, if it is left in water for 24 hours or more, especially 76 hours, it will give perfect results regardless of the particle size. Further, it is preferable to keep the temperature at which the product is left standing at 20° C. or higher.

Then leave it to dry. This drying should be done as long as the water on the powder surface is drained, and the drying should be done to the extent that the crucible does not crack and the powder does not scatter, so as to prevent the initial slang caused by the transition to the high temperature of the first firing process. If it is good. Therefore, drying can be carried out from air drying to a temperature range where the zinc powder does not melt. Next, the dried powder is placed in a crucible made of alumina, etc., and heated to a temperature of 150°C in an atmosphere containing oxygen.
Heating at 0°C, particularly 900-110°C, gives good results for any particle size.

The heating and firing described above may normally be carried out in air, but may also be carried out in a mixed gas of nitrogen and oxygen.

As mentioned above, an oxide film is formed on the surface of metallic zinc powder when mechanical pressure is applied to it in the presence of water, such as by rolling or rolling, but this film is formed when left in water afterwards. A film grows. This was confirmed by X-ray diffraction. The oxide film thus formed also provides special effects. That is, in the case of a product having a thin passive film that is normally formed on the surface of zinc in a dry atmosphere, the firing process will be uneven, resulting in the coexistence of nodular zinc oxide and metallic zinc.

On the other hand, in the zinc powder with the above-mentioned grown oxide film,
High temperature firing progresses uniformly and completely.

Metallic zinc is completely oxidized and grows into zinc oxide whiskers at a high rate. In addition, during high-temperature formation, the reaction of the original slope installed inside the vessel ends inside the vessel.

Also, is it possible that [the whiskers produced are simple compared to those seen in conventional zinc oxide whiskers?] ! It has a tetrabod-like structure with a needle-like crystal structure that has grown into four rings from the core, rather than a fibrous single crystal.

The basic shape of the zinc oxide whiskers is a tetrabod-like 1J structure, but many have a triaxially grown needle-like crystal structure. This is subjected to secondary processing 1, for example, using a ball mill.
After time crushing, cut from the base of the crystal growth axis,
Of course, it is possible to use rod-shaped needle-shaped zinc oxide.

Now, by adding glass frit to this zinc oxide whisker and firing it at a temperature above the melting point of this glass frit, a υ filtration filter was obtained.

The characteristics and amount of zinc oxide whiskers, the amount of glass frit added, the melting point, and the firing temperature were as shown in Table 1 below.

(The following is a blank space) In Examples (1), (2), and (3), polyvinyl alcohol was used as a binder during molding, and the press pressure was 200'C9/cITl.

Table 2 below shows the implementation columns (1), (2), (3) and the conventional example (brown).

(6) This is the result of conducting actual filtration tests under certain conditions and examining the filter characteristics.

(4), (5), and (6) are filter paper, membrane filter, and nickel sintered metal filter, respectively. still.

For filter characteristic evaluation, polystyrene gel having an average particle size of 3 μm was dispersed in pure water.

The case of US 1F paper was set as 1.

As described above, the examples have high water permeability under low pressure and change even more significantly under high pressure, exhibiting excellent filter properties 2. still,
At this time, the rejection rate of polystyrene gel was 100% for each filter.

As a result of the effects of the invention, the filtration filter of the present invention is extremely stable even under high pressure, exhibits high water permeability, and has extremely high filtration efficiency), and has great industrial potential.

Claims (1)

[Claims] A filtration filter characterized by being made by adding glass frit to zinc oxide whiskers having a structure branched in two or more directions and firing the mixture.