JPH0360710A - Filter medium for purifying air - Google Patents

Abstract

PURPOSE:To obtain a filter medium fit to purify air contg. salts as solid matter, etc., by using highly acidic ion exchange fibers, highly basic ion exchange fibers and fibers other than ion exchange fibers and specifying the diameter of each of the fibers. CONSTITUTION:When a filter medium is obtd., highly acidic ion exchange fibers of 1-50mum diameter, highly basic ion exchange fibers of 1-50mum diameter and fibers of 0.1-10mum diameter other than ion exchange fibers are used and the diameter of >=70wt.% of the fibers other than ion exchange fibers is regulated to <=1/10 of the average diameter of the highly acidic and highly basic ion exchange fibers. In the case where air contg. salts as solid matter or fine particles of a soln. is filtered with the resulting filter medium, the intrusion of salt by rescattering phenomenon and pressure drop are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is a filter medium containing specific ion exchange fibers,
The present invention relates to a filter material for air purification containing salts as solid or solution particles.

(Conventional technology) Recently, the number of industries that require ultra-clean spaces is increasing.
It is no exaggeration to say that clean room technology is now required in most industries. Here, as a method of collecting particulate matter floating in the air and obtaining an ultra-clean space, a filtration and dust collection technique using an air purifying filter material is generally used. This is a technology that collects dust by passing outside air through several types of filter media with different collection efficiencies. At present, the technology for collecting fine particles, which are always solid, has reached a very advanced level.

However, substances suspended in the air are not always solid; there are other liquid particles in the air, such as ξst, which deliquesce and easily liquefy due to an increase in relative humidity. It may also contain fine salt particles.

These salts originate from the bursting of bubbles caused by waves in the ocean, and are also called sea salt particles (Norio Isahaya et al. Comprehensive Technology for Measurement and Control of Suspended Particulates for Air Purification Chapter 3, 10) The presence of sea salt particles is a major problem in Japan, which is surrounded by the ocean on all sides and has no choice but to locate production bases in coastal areas.

When treating air containing floating sea salt particles using conventional air purification filter media, the sea salt particles caught on the filter media liquefy as the relative humidity increases, and become trapped inside the filter media. This is because a so-called re-scattering phenomenon occurs, which is a phenomenon in which particles penetrate and then fly out downstream again. In a semiconductor manufacturing clean room, salt that enters the room by re-splattering is deposited on semiconductor wafers and becomes a major cause of yield reduction including poor insulation. In addition, even in today's office buildings that use many computers and OA equipment, empty! Sea salt entering through the Ja vessel is a major cause of troubles due to corrosion of connectors. In addition, the sea salts captured on these filter media absorb moisture and undergo deliquescence during operation of the air filtration system, and solidify or deliquesce to become a highly viscous liquid, increasing the pressure (l loss). Therefore, air conditioning equipment such as clean rooms built in coastal areas is equipped with various salt removal measures.The method is to heat the air, lower the relative humidity, and filter the air in a dry state. or by spraying pure water into the air.
Methods include turning sea salt into droplets, enlarging the particle size, and filtering with a water-repellent filter material, passing air through a pure water scrubber, and combinations thereof. However, these methods have the disadvantage that equipment costs and operating costs are enormous. In addition, methods have been adopted to delay the occurrence of re-entrainment by making the filter medium thicker or multi-layered to increase the amount of mist retained, but this is not a fundamental solution and also reduces the pressure loss of the filter medium. This also causes the problem of increased operating costs.

A method of using ion exchange fibers as an air filtering material has already been reported in Japanese Patent Laid-Open Publication No. 12315/1983. The above publication describes the use of a filter for air purification equipment in which ion-exchange fibers are mixed with glass 111 fibers having a smaller diameter than the ion-exchange fibers to remove contaminants such as particulate matter, acid gas, alkaline gas, and odorous gas in the gas. It is described that it collects and removes substances. However, the above-mentioned publication does not describe the above-mentioned problems and their solutions when treating air containing solid or liquid fine particles of salts. Examples of the above publication disclose, for example, an air purifying filter containing an anionic fiber having a quaternary amino group, a cationic fiber having a sodium carboxylate group, and glass fiber. However, according to studies by the present inventors, this filter cannot exhibit sufficient effectiveness when capturing salt particles and sea salt particles contained in the atmosphere.

(Problems to be Solved by the Invention) When filtering air containing solid or solution particles of salts, it is an object of the present invention to solve the problem of salts due to the re-entrainment phenomenon, which is a phenomenon in which salts leak to the downstream side of the filter medium as described above. It is an object of the present invention to provide a filter medium in which there is little intrusion of water, and the increase in pressure loss of the filter medium is small.

(Means for Solving the Problems) The present invention provides strong acidic ion exchange fibers (a), strong basic ion exchange fibers (9), and fibers other than ion exchange fibers (c).
, wherein the fibers (a) and (b) have a diameter of 1 to 50 μm, and 70 wt% or more of the fiber (c) is (
a) and (having a diameter of 1/10 or less of the average diameter of bl,
The present invention relates to an air purifying filter material containing salts as solid or liquid particles.

Ion exchange fibers made of organic polymer compounds are easily available as the ion exchange fibers used in the present invention.

As base fibers for organic fibers having an ion exchange function, there are known types such as cellulose-based, polystyrene-based, vinylon-based, phenol-based, and nitrile-based fibers. Among these, nitrile fibers are preferred from the viewpoints of ease of producing long fibers during spinning, flexibility and strength of fibers, and ease of introducing ion exchange groups.

The ion exchange functional group can be introduced into these base fibers by a known method. Here, the functional group of the strongly acidic ion exchange fiber is generally a sulfonic acid group, and the functional group of the strongly basic ion exchange fiber is generally a quaternary ammonium group. When the ion exchange fiber used in the present invention adsorbs neutral salts such as sea salt, its exchange capacity is preferably above a certain level from the viewpoint of adsorption effect and life as an ion exchange filter material. Salt ion exchange capacity is 0.5 m
eq/g - ion exchange fiber or more, more preferably 1.
It is preferable that it is more than Omeq/g of ion exchange fiber.

Fibers other than ion-exchange fibers used in the present invention include organic, inorganic, and metal wJ&fibers, but are not particularly limited. Specifically, natural fibers include cotton, linen, wool, etc.; recycled and half-metal TM fibers include rayon, cellulose, acetate, etc.; and a combination TM fibers include polyamide, polyimide, polyvinyl alcohol, polyvinyl chloride, polyacrylonitrile, polyester, Polyolefin, polyurethane, polysulfone, polycarbonate, polyester ether, etc.; inorganic fibers include glass fiber, carbon fiber, activated carbon fiber, alumina fiber ring; metal fibers include steel wool, etc. Furthermore, synthetic fibers mixed with or coated with conductive carbon products or the like may also be used. Glass fibers can be produced relatively easily with submicron diameters, and have sufficient strength, rigidity, and workability, making them the best material for forming air filtration media.

In order to obtain sufficient performance as an air filtration material, the diameter of the fibers used is an issue, but due to manufacturing process issues, ion-exchange m-fibers have a diameter that is not normally used for air filtration materials. They are often thicker than the fibers that are present. In this way, a filtration material containing many thick fibers cannot fully demonstrate the filtration performance when microscopic dust of 0.5μ or less inflows, so the filtration material of the present invention uses ion-exchange fibers and Used in combination with other thin fibers.

The mm diameter of the ion exchange fiber is 1 to 50 μm, preferably 1
~20 μm is preferable. The fiber diameter of fibers other than ion-exchange fibers varies depending on the target collection efficiency of the filtration medium, pressure loss, etc., but in order to obtain sufficient collection efficiency, it is necessary to
It is preferable that it is 1-10 micrometers.

The diameter of fibers other than ion exchange fibers is 70-1
It is desirable that at least % of the ion exchange fibers have a diameter of 1710 or less of the average diameter of the ion exchange fibers. By combining these m-fibers, the collection efficiency is improved by fine $11!1, and the captured mist is quickly transferred to the ion-exchange fibers, so that the ion-exchange function can be maximized.

The combination in the filter medium of the present invention includes not only uniformly mixing each fiber in advance and processing it into a filter medium, but also superimposing filter materials obtained by processing each fiber separately.

Although the method for producing the filter medium is not limited, examples of the method for producing the sheet-like material include a wet papermaking method, a dry papermaking method, and the like.

In the present invention, it is desirable to insert a binder substance in order to maintain the strength of the filter medium and prevent the filter medium from collapsing. Examples of the binder include fibrous binders, particularly thermoplastic organic polymer fibers, and a high-performance filtering medium can be obtained by a hot-melt manufacturing method using this binder. In the filter medium of the present invention, the greater the content ratio of ion exchange fibers, the longer the life of the filter medium, but the lower the solid particulate collection efficiency. For example, when glass fibers are used as fibers other than ion-exchange fibers, it is desirable that the proportion of ion-exchange fibers be within 70% of the total weight of the overmaterial. Furthermore, in this case, taking into account the life of the filter, etc., the proportion of ion exchange fibers is suitably about 50 to 70%.

It has been found that in the filter medium of the present invention, the best ratio of the strongly acidic ion-exchanged $a fibers and the strongly basic ion-exchanged fibers is such that the exchange capacities of both fibers are equal. However, this ratio may be changed depending on the properties of the air to be filtered. For example, when filtering air in an industrial area containing gaseous substances such as sulfur dioxide gas, the amount of strong basic ion exchange fibers may be changed to a certain extent. The amount of strongly acidic ion exchange fibers may be increased, or conversely, it may be desirable to increase the amount of strongly acidic ion exchange fibers.

However, it is necessary that the strongly acidic ion-exchange fiber and the strongly basic ion-exchange fiber coexist, and it is desirable that the ratio of the exchange capacity is within 1:0.5 to 2.

The salts floating in the air are mainly Na and C.
Examples include chlorides such as aMg, sulfides, carbonates, and salts of various metal elements.

In addition to the above, ionic substances such as nitrates, ammonium salts, and gaseous substances are present in the air, and the filter medium of the present invention allows them to be simultaneously separated by ion exchange.

The filter medium of the present invention is suitable for removing these salts from air containing 1 to 50.000 μg 7 m 3 of these salts as solid or liquid fine particles.

The ion exchange function of the filtration device of the present invention is maximized when the salt mist is in liquid form and when the relative humidity in the gas is high. However, in the case of dry air filtration and solid salt particle filtration, the present filter material has exactly the same performance as commonly used air filter materials. In other words, this filter material has the same performance as a conventional filter material when dry air is being filtered, and when humid air enters the filter material, there is no deterioration in the function of a normal filter material caused by re-scattering.

A feature of this filter material is that it can effectively and automatically respond to changes in air conditions due to changes in the weather. Here, in order to maximize the performance of the filter medium, it is not prohibited to apply a certain level of humidity to the air. Examples of methods for imparting a certain level of humidity to air include air-liquid contact methods such as bubbling air into water and spraying water, or spraying or dripping water onto the filter itself.

Furthermore, a major feature of this filter material is that it is possible to suppress the increase in pressure loss by using both anion and cation exchange fibers at the same time. , highly deliquescent potassium chloride, magnesium chloride, and ammonium chloride are captured on the filter medium. These substances either absorb moisture and solidify during the use of the permeable material, or deliquesce and become extremely viscous liquids, increasing the pressure loss of the filter material (edited by the Japan Powder Industry Association: Bag Filter Handbook 125).
P etc. may be helpful. ) 0 Since the salt captured on the filter medium of the present invention deliquesces and is chemically captured within the fibers through ion exchange, there is little increase in pressure loss due to the above reasons. like,
This is noticeable when installed in an environment where the air contains many salt particles.

(Effects of the Invention) The air purifying filter material of the present invention can be applied not only to the treatment of air taken into buildings and equipment, but also to the treatment of circulating air within buildings and equipment, or to the treatment of released air. When used, it efficiently collects fine particles (aerosols) suspended in the air, especially fine particles of ionic substances such as sea salt and low-salt substances, and chemically fixes them to prevent them from being re-dispersed. It can effectively follow changes in outside environmental conditions such as weather, and reduce the amount of salt flowing into the latter stages of the filtration system. Furthermore, due to the effect of ion exchange, it is possible to suppress the increase in pressure caused by ionic components.

(Examples) The present invention will be specifically explained using the following examples, but the present invention is not limited thereto.

Example 1 Polyacrylonitrile fiber, strongly acidic ion exchange fiber with sulfonic acid group (fiber diameter 20μ) 35wL%, strongly basic ion exchange fiber with quaternary ammonium group (fiber diameter 20μ) 35i+t%, Glass fiber (fiber diameter 1
μ) 23 wt% and thermoplastic binder fiber (fiber diameter 1
0μ) 7wt%, the thickness was approximately 0.0μ by wet paper making method.
am, a filter medium with a porosity of about 90% was produced. This is a medium performance filter with a pressure drop of 4.7 - water columns and a particle size of 0.3 microns and a DOP (dioctyl phthalate) particle permeability of less than 50%. Using this filter, a filter material (a) having ion exchange ability and a filter material saturated with NaCl and having no ion exchange ability (b) were prepared.

In addition, instead of the above-mentioned ion-exchange fiber, a polyacrylonitrile-based weakly acidic ion-exchange fiber 3 having the same fiber diameter may be used.
A filtration material equivalent to a medium-performance filter (c) was prepared in the same manner except that it contained 5-t% and weakly basic ion exchange fibers 35wt%.
was created. The filtration performance of these three sheets was compared. There is no difference in DOP trapping efficiency between these, but as shown in Table 1, there is a large difference in salt trapping ability. This is Na
A 0.3% solution mist of C+ (median diameter approximately 2μ) was applied at a Na″ concentration of 5000μg/m3 and a flow rate of 5.3cm/sec.
The ion concentration in the gas on the outlet side was measured over time.

The Na'' and C1- concentrations were collected using an inbinger using pure water, and were carried out by atomic absorption spectrometry and ion chromatography, respectively.

It can be seen that the combination of weakly acidic and weakly basic fibers has almost the same ability as fibers that have no exchange ability at all.

Inlet/Outlet Example 2 A medium-performance filter similar to the filter material (a) of Example 1 was prepared with a different content of ion exchange fiber.
The exchange capacity of both ion exchange fibers is approximately 1 meq/g-I
Since they are almost equal in EF (ion exchange fiber), always use the same amount, and the total weight ratio of both ion exchange fibers in the filter medium is 0%.
, 20%, 50%, 70%, and 100%. Figure 1 shows the results of investigating the filtration performance of a 0.3% solution mist of NaCl (median diameter approximately 2μ) using these materials. c.
+*/sec and the test time is 8 hours. From this result, it can be seen that the abundance ratio of ion exchange fibers in the filter medium is preferably around 70%.

Example 3 A medium-performance filter similar to the filtration (a) of Example 1 was prepared, and this filter was saturated with NaCl to eliminate the ion exchange ability. Using both of these flat membrane filtration media, N
0.3% solution mist of aC1 (median diameter approx. 2μ) was mixed with Na″
Concentration approximately 10,000 u g/m”, flow rate 5°3 cm/s
Filtered with ec. At this time, the temperature was 20'C.

Relative humidity was 90%. Every 2 hours, dry air (temperature 20°C 1 relative temperature 20% or less), in the order of 8
filtered for hours. The final pressure drop was 4.7 am water column for the filter medium with ion exchange capacity, which is equal to the initial pressure drop, whereas the filter medium without ion exchange capacity was 11 m water column.

[Brief explanation of drawings]

Figure 1 shows the abundance ratio of ion exchange fibers in the filter medium and NaC
1 is a relationship diagram with the collection efficiency of one solution mist. Coughing efficiency (〆nt J order)

Claims (1)

[Claims] A filtration medium comprising strongly acidic ion exchange fibers (a), strongly basic ion exchange fibers (b), and fibers other than ion exchange fibers (c), wherein the fibers (a) and (b) have a diameter of 1 ~5
0 μm, the diameter of the fiber (c) is 0.1 to 10 μm, and 70 wt% or more of the fiber (c) is composed of the fibers (a) and (
A filter material for purifying air containing salts, which has a diameter that is 1/10 or less of the average diameter of b).