JPH07110326B2 - ▲ Ro ▼ over filter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a water treatment filter for soil treatment, fresh water, etc., an air purifying filter, a suspension treatment filter for the food industry, water for the chemical industry, drainage process filter. For overfilters used as

Conventional technology Conventional overfilters are made by entwining organic fibers such as paper, cloth, etc., connected by another kind of binder such as non-woven fabric, wire mesh, glass mat, glass cloth, fine wire, inorganic fiber. Entangled with each other or connected with a binder, organic sheet-like material with network pores and fine pores developed, inorganic non-fibrous granular material such as sintered metal welded or connected with another kind of binder Etc.

Problems to be Solved by the Invention These have their respective characteristics, but in terms of over-efficiency, if the diameter of the fibrous material is small,
The permeability is good, but under high pressure, the fiber part is deformed to be consolidated and the permeability is lowered. However, even at low pressure, the pore formation density is limited and the permeability is inferior to the former. Also, under high pressure, the pore size changes due to consolidation, and the transmittance decreases.
The pore size does not change under low pressure and high pressure, but the porosity does not increase sufficiently.

The present invention is intended to provide an overfilter that achieves a high rejection rate and a high permeability both under normal pressure and under high pressure by improving the deterioration of overcharacteristics under high pressure, which is a problem of various conventional filters. is there.

Means for Solving the Problems The present invention is one in which a glass frit is added to a zinc oxide whisker having a structure branched in two or more directions, followed by firing.

Working The needle-shaped portions of the above whiskers are entangled with each other, and an extremely excellent material structure having pores and high porosity is achieved. The pore size is reduced by the pressing pressure during molding, and the intersections of the needle-shaped parts are connected by melting the added glass frit. Further, the above whiskers have good wettability with water, solvent, etc., and are a single crystal material having a strength close to a perfect crystal strength with no internal lattice defect, and exhibit no excessive changes even under high pressure and exhibit over-characteristics. It is a thing.

Examples Examples of the present invention will be described below.

First, a zinc oxide whisker manufactured by oxidizing metallic zinc is prepared. More specifically, this zinc oxide whisker is obtained by using metallic zinc powder, which is different from the conventional methods for producing zinc oxide and zinc oxide whiskers. A particle size of 0.1 to 500 μm can be used, and a particle size of 10 to 300 μm gives the best result. Further, these metallic zinc powders are preferably powders obtained by spraying zinc wires or zinc powders into the air with an arc-type spraying device, but they can be obtained by other pulverizing methods, atomizing methods, stamp mill methods, ball mill methods. Zinc powder in the above range can also be used.

As a method for forming an oxide film on the surface of the zinc powder, the following method is preferable. First, as mechanical treatment in the coexistence of water, treatment is carried out with a milk needle type pickling machine, rolls, etc., and mechanical pressure is applied to the particles. Furthermore, it gives complete results in particles of any size for more than 24 hours, especially 76 hours. Further, the standing temperature is preferably maintained at 20 ° C or higher. Next, it is left to dry. This drying only needs to be carried out so that the surface of the powder can be drained, and the drying should be carried out so as to prevent the initial damage caused by shifting to high temperature in the next firing step, that is, to the extent that crucibles, cracks, and scattering of powder do not occur. If it is good. For this reason, it is possible to perform from air drying to a temperature range where the zinc powder is not melted. The dried powder is then placed in a heat-resistant container, usually a crucible such as alumina, and heated in an atmosphere containing oxygen at 600 to 1500 ° C, especially 900 to 1100 ° C, to give good results with any particle size.

The above heating and firing may be normally performed in air, but may be performed in a mixed gas of nitrogen and oxygen.

As described above, an oxide film is formed on the surface of the zinc metal powder by applying mechanical pressure with a roller or the like in the presence of water as described above, but this film grows after being left in water later. . This was confirmed by the X-ray diffraction method. Further, the oxide film thus formed has a special effect. That is, in the case of a material having a thin passivation film that is usually formed on the surface of zinc in a dry atmosphere, it becomes non-uniformly fired at the time of firing, and zinc oxide and metallic zinc coexist.
On the other hand, in the zinc powder having the above grown oxide film,
The high temperature firing progresses uniformly and completely, the metallic zinc is completely oxidized, and the zinc oxide whiskers grow at a high rate. Further, during the high temperature firing, the reaction of the raw material placed inside the container is completed inside the container. Also, the whiskers generated here are
It is not a simple fibrous single crystal found in a conventional zinc oxide whisker, but has a tetrapod-like structure having a needle-like crystal structure grown from the nucleus in four axes.

The zinc oxide whiskers have a tetrapod-like structure as a basic shape, but many of them have a triaxially grown needle-like crystal structure. It is, of course, possible to carry out secondary processing, for example, crushing with a ball mill for 24 hours and cutting from the root of the crystal growth axis to obtain rod-shaped acicular zinc oxide.

A glass frit was added to the zinc oxide whiskers and the mixture was baked at a temperature equal to or higher than the melting point of the glass frit to obtain an overfilter.

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

In Examples (1), (2) and (3), polyvinyl alcohol was used as a binder at the time of molding and the pressing pressure was 20.
It was set to 0 kg / cm ² .

Table 2 below shows that Examples (1), (2) and (3) and Conventional Examples (4), (5) and (6) were subjected to over-experimentation under constant conditions.
This is the result of examining the filter characteristics.

(4), (5) and (6) are a paper, a membrane filter and a nickel sintered metal filter, respectively. The filter characteristics were evaluated by using polystyrene gel having an average particle size of 3 μm dispersed in pure water.

As described above, the examples have a large water permeability under low pressure, and further greatly change under high pressure, and show excellent filter characteristics. still,
At this time, the rejection rate of polystyrene gel was 100% in each of the filters.

EFFECTS OF THE INVENTION As described above, the overfilter of the present invention is extremely stable even under high pressure, exhibits high water permeability, and has a significantly high overefficiency, and is highly industrial.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Eizo Asakura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Minor Yoshinaka, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References Japanese Patent Laid-Open No. 1-215325 (JP, A)

Claims (1)

[Claims] 1. An overfilter which is obtained by adding glass frit to a zinc oxide whisker having a structure branched in two or more directions and firing the glass frit.