JPS60225619A - Liquid filter material - Google Patents

Abstract

PURPOSE:To obtain an inexpensive filter material having high removal efficiency, by adsorbing and removing particles having a small particle size by the electrostatic adsorbing action of a perforated material to which a charged substance was adhered. CONSTITUTION:In using a fiber as the constitutional material of a perforated material 3, a polyester fiber 1 with a thickness of 0.1 denier and a polyester fiber with a thickness of 1.1 denier melted at about 200 deg.C are mixed in a ratio of 8:2 and the resulting mixture is formed into the perforated material 3 having a basis wt. of 50-150g/m<2> by a papermaking process and heated to mutually adhere the fibers. As a charged substance, aluminium hydroxide, iron oxide or a high-molecular flocculant are used. In the case aluminum hydroxide, the perforated material 3 is impregnated with a 1-10% aluminum chloride solution and, after the impregnated one is dehydrated so as to leave about 200% of said slution, neutralization treatment is applied thereto by sodium carbonate to form aluminum hydroxide particles which are, in turn, adhered to the surfaces of the fibers by the charge thereof.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a filter material for removing particles contained in a liquid, and provides a filter material with extremely high removal efficiency. The purpose is to

(Conventional technology) For products such as LSI semiconductor devices, where dust adhesion during the manufacturing process can significantly reduce performance or shorten life, it is used to purify the air in the manufacturing environment and to clean semiconductor substrates and other objects. Although there is a strong demand for water purification, the recent miniaturization of devices in particular requires even more sophisticated air and water purification. Various studies have been conducted in this regard, and the present inventor has conducted research on air purification.
An example that satisfies this requirement is a dust collection efficiency of 99999.
9% or more, that is, ",'] 00%, and although it has extremely high dust collection efficiency, it is an extremely practical air contact with a cross-section force loss that is almost the same as or less than that of conventional high-performance products. The paper has made a major contribution not only to the semiconductor manufacturing industry mentioned above, but also to a variety of other uses, such as making radioactive exhaust air non-radioactive.

(Problems with the prior art) However, with the current technology for water purification, it is impossible to remove fine particles smaller than the particle size of The maintenance costs required for replacing filter media due to clogging are high;
The present situation is unsatisfactory, as the pressure drop becomes extremely high, making it difficult to feed the liquid to be purified (1), and significantly slowing down the processing speed.

In other words, the liquid filtration materials that have been developed to date include sintered metal particles, paper made from fibers such as cellulose, synthetic resin, and asbestos, and synthetic resin films with holes made with electron beams. This is the so-called bore type, in which foamed material is mixed in during the production of synthetic resin film, which is degassed by heating to form pores. The aim is to create a filter that clearly blocks the passage of particles and removes them. However, when using sintered metal, there are restrictions based on the size of the metal particles, and when using fibers, there are restrictions based on the fact that the diameter of the fibers cannot be made smaller than the specified thickness. It is not possible to create a filter medium with the required removal efficiency that can create a hole for the passage of water. Therefore, at present, the mainstream is a synthetic resin film with holes, but due to technical constraints, Komei cannot make the hole diameter smaller than the current size. Therefore, it is impossible to hope for a removal efficiency higher than the current level; or even if drilling were to be achieved, the pressure loss would be significantly lower as the diameter of the hole becomes smaller. There are limits to the removal efficiency that can be achieved. In addition, in the case of liquid filter media, the final ideal is for the particles in the liquid that pass through the filter to be reduced to zero, but holes with a diameter smaller than the particles to be removed are provided to prevent particles from passing through. In the case of filters based on the principle of filtering, it is possible to reduce the flow to zero unless the pores are removed, which would make it impossible for liquid to flow and fundamentally lose its function as a liquid filtering material. Therefore, with this conventional approach, it is theoretically impossible to realize a liquid filter material with low pressure loss and 00% removal efficiency.

The present invention realizes a high-performance and inexpensive liquid filtration material that is difficult to realize with current technology, improves performance by highly purifying the washing water for semiconductor devices, and further improves radioactivity. This system is designed to contribute to thorough pollution prevention by making waste liquid radioactive. Next, the present invention will be explained in detail using the drawings.

[Structure of the invention]

3- (Means and effects for solving the problems) The present invention is characterized by breaking away from the conventional fixed idea that the removal of fine particles relies only on liquid flow holes.

In other words, particles with a particle size smaller than or equal to the particle size are removed by blocking the second liquid flow hole having a diameter smaller than the particle size, and particles with a particle size that passes through the liquid flow hole are removed. For example, charged substances such as activated and charged inorganic substances such as aluminum hydroxide and iron hydroxide, and organic polymer flocculants such as polyacrylamide, acrylic ester, and sodium alginate can be used. It is characterized by being able to achieve the purpose by using both mechanical and electrostatic properties, by adsorbing and removing substances by utilizing the electrostatic adsorption effect of the substance. Paper fibers, metal sintered bodies, wire mesh, etc. can be used as necessary, and the charged substance can be attached to these by, for example, the following method.

In the case of water filtration media that uses fibers as the constituent material of the porous material, polyester fibers with a thickness of 0.1 denier and approximately 2
Polyester fibers with a thickness of 1.1 denier 4- which melt at 00''C are mixed at a ratio of 8:2 (weight ratio) to form a paper of 50~]-50gr/rri' and then heated. A porous material is formed by bonding the fibers together.

Next, this is impregnated with a ~10% solution of a metal salt such as sodium aluminate or aluminum chloride, and after absorbing and dehydrating it so that about 200% remains in the porous material,
For example, this is neutralized with sodium carbonate, which has alkaline properties, to generate electrically charged aluminum hydroxide particles, which adhere well to the surface of the fibers due to their charge, and are then thoroughly washed with water to prevent them from flowing out during filtration. Remove remaining inorganic substances.

For example, when attaching iron hydroxide to the surface of fibers, for example, the paper-made fibers are impregnated with a 1 to 10% aqueous solution of iron sulfate, and then neutralized with sodium carbonate to charge the surface of the fibers. This is done by depositing iron hydroxide on the aluminum hydroxide, followed by thorough washing with water. In these cases, the neutralization reaction produces charged aluminum hydroxide particles, so it is necessary to ensure that the neutralization reaction lasts for a long time. It is important to consider the characteristics and concentration of the neutralizing agent to strengthen the charge and improve the adsorption performance.

Further, when an organic flocculant is used to impart chargeability to the porous material, it is preferable to select a flocculant that is soluble in water.

In this way, it is possible to obtain a high degree of removal action while selecting the diameter of the liquid flow hole in the porous material so as to obtain the desired pressure loss, and if the electrostatic adsorption action is perfect, then In principle, it is possible to provide a filter material that has low pressure loss and can reduce the number of particles in the liquid after passing through the filter material to zero. In addition, it is only necessary to attach a charged substance to a porous material, and there is no need to use the conventional method of making small holes in a synthetic resin film, so we can provide a liquid filtration material with high removal efficiency at a low cost. This reduces the cost of replacing filter media. Next, examples of the present invention will be described.

(Example) As shown in the figure, 80% 0.1 denier polyester fiber
(weight ratio) (1) and l for binder that melts at 200℃
] Denier polyester fibers 20% (weight ratio) (2) are made into paper at 50 gr/m2 and heated to form a porous material (3) in which the denier polyester fibers are bonded together. Then, this is impregnated with a 1% aqueous solution of sodium aluminate and dehydrated so that about 200% remains in the filter medium. Next, the aluminum hydroxide layer (4) is attached to the surface of the fibers by neutralization with sodium carbonate, and the inorganic substances existing in an unstable state on the surface of the fibers are removed by washing with water. 1 defense against flowing out.

Table 1 shows that the filtration material of the present invention made as described in 1) and 2 and the conventional filtration material to which aluminum hydroxide does not adhere, which is made using fibers equivalent to those of the present invention, are laminated, respectively.
Particles as shown in Table 2 were mixed into these (
], number of contaminants per Oc c), filtration area of cooling water used for cutting semiconductor substrates] 0.04 l/mi per d
This is a comparison of the results obtained when the sample was passed at a flow rate of n. It is clear from this that the surface color of the conventional filter material is 0
Both sheets are colored brown or light brown, indicating the presence of particles in the liquid that has passed through the filter medium. However, in the case of the present invention, only some of the two filter media are colored brown or light brown, while the other eight filter media are not colored and the particles in the liquid that have passed through the filter media are zero. , or very few. In addition, when we counted the particles in the liquid that passed through the filter medium using a Tendal-type particle measuring device with a particle size of 05μ, we found that with the conventional filter medium, the number of particles in Oc c (]O times The average of the measurements was about 10,000 points, whereas the filter material of the present invention had about 10 points, which shows that the filter material of the present invention has an extremely high removal rate. Also, with the conventional filter material, the filtration area is 1c at a flow rate of 0.04e/min.
r! The initial pressure loss per unit is 0. I Kp, whereas in the present invention it is 0.15 Kf, which is within a practical range. However, the increase in pressure loss in the present invention is caused by the aluminum hydroxide attached to the surface and the smaller liquid flow holes. Therefore, if the thickness of the fibers forming the porous body is changed so that the diameter of the liquid flow hole is the same as that of the conventional one when aluminum hydroxide is attached,
Pressure loss can be made equal to that of the conventional method. Furthermore, by adjusting the thickness of the fibers and the thickness of the charged substance attached, it is possible to further reduce the pressure loss.

As described above, the present invention has been described in two ways. Depending on the properties of the liquid to be filtered, by selecting the properties of the charged substance to be attached and the material of the porous material, it is possible to prevent the charged substances from falling out or forming By preventing the pores from dissolving, it is possible to filter liquids other than water, such as oil and alkaline liquid, with high removal efficiency.

(Effects of the invention) As is clear from the above explanation, the present invention provides a liquid filter material that has a high removal effect, low pressure loss, and is inexpensive. It makes a major contribution to purification.

[Brief explanation of drawings]

The figure is a schematic diagram of the structure of the liquid filtration body of the present invention. (1) Main constituent fibers, (2) Fiber for binder, (3) ... Perforated material, (4)...Charged substance layer. Patent applicant Yoshimi Shinobu 11- -12~ Supplementary Procedures (Method) %formula% I Incident display Special application 1984. -No. 80156 2 Name of the invention liquid filtration media 38 Person who makes amendments Relationship to the case: Applicant Shinobi Ashigi See 4. Agent Nishi-Shinjuku, Shinjuku-ku, Tokyo], -23-1 5 Date of amendment order July 31, 1980 (shipped) 6. Subject of correction “Detailed description of the invention” column in the specification

Claims (1)

[Claims] A charged substance is attached to a porous material, the liquid flow holes of the porous material make it clear that particles in the liquid larger than the diameter of the hole pass through, and the particles having a particle size that passes through the liquid flow holes are adsorbed by the charged substance. A liquid filtration material characterized in that the liquid is captured on a filtration assembly.