JPS58163489A - Removal of suspended fine particle from aqueous liquid contg. acid, alkali or/and oxidizing agent - Google Patents

Abstract

PURPOSE:To effectively remove suspended fine particles, by treating an aqueous solution contg. alkali or (and) an oxidizing agent with a hollow fiber of resin, e.g. polyolefin, comprising a microporous membrane having specified porosity and average pore size. CONSTITUTION:A hollow fiber of polyolefin or polyfluoric vinylidene resin having an inner diameter of 0.05-5mm. and film thickness of 0.03-2mm. is formed from a porous membrane having porosity of 15-90% and average pore size of 0.01-5mum. The aqueous solution of one or more acids, e.g. sulfuric, acetic, phosphoric, nitric, hydrochloric and hydrofluoric acids, alkali, e.g. caustic soda, or (and) an oxidizing agent, e.g. hydrogen peroxide or sodium hypochlorite, is filtered by letting it flow through the hollow fiber comprising said porous membrane, to remove suspended fine particles from said aqueous solution. This method is can be esp. suitably applied for refining a chemical agent to be used in the semiconductor industry.

Description

[Detailed Description of the Invention] In recent years, inorganic chemicals such as acids and alkalis have been used to remove suspended fine particles in aqueous liquids! There is an increasing need to do this.

Specifically, a hydrofluoric acid solution is used for silicon wafer etching during semiconductor manufacturing, but if suspended particles remain in this solution, it will affect the subsequent product yield. In recent years, as integrated circuits have become more wrinkled, the degree of their influence has become even greater.

On the other hand, many porous membranes have been used to remove suspended particles in aqueous liquids, but none of them
In alkaline aqueous liquids, long-term use often leads to unsatisfactory results.

For example, the most widely used cellulose acetate membrane has a significantly short lifetime due to its chemical degradation. Furthermore, since the surface energy of Teflon membranes, which have high chemical resistance and extremely low surface energy, the amount of water filtration decreases rapidly during use, making them unsuitable for long-term use.

As a result of extensive research, the inventors have developed a porous membrane that can effectively remove suspended fine particles in an aqueous solution containing acids, alkalis, or Fi (and) oxidizing agents, and can withstand long-term use. The following invention was achieved.

That is, an aqueous liquid containing an acid or alkali or (and) an oxidizing agent is mixed with a porosity of 15 to 90%, an average pore size of 0, and an O of 1 to 5μ.
It is made of a porous membrane having an inner diameter of 0.05~g■ and a film thickness of 0.
It has been found that suspended fine particles in the aqueous liquid can be effectively removed by passing through filtration through a polyolefin or polyvinylidene fluoride resin hollow fiber having a diameter of 03-2.

The porous membrane does not have defects like the previously mentioned membranes on the market, and can remove suspended fine particles extremely efficiently.
Moreover, it can withstand long-term use and can make a great contribution to related users.

The pore diameter Vi of the multi-porous membrane is required to be in the range of 0.01 to 5μ in terms of filtration performance. Furthermore, the porosity must also be between 15 and 90%.

The hollow fibers made of the porous membrane may contain a polyolefin resin such as polyethylene, polypropylene, polybutylene, or a mixture of 2111 or more of the above, or a copolymer made of a mixture of two or more of ethylene, propylene, butene, hexene, and tetrafluoroethylene. Coalescence etc. or polyvinylidene fluoride resin is adopted.

- Aqueous liquids containing acids or alkalis or Fi (and) oxidizing agents that can be applied to the present invention include sulfuric acid, acetic acid, phosphoric acid, nitric acid,
One or more acidic aqueous liquids such as hydrochloric acid and hydrofluoric acid, alkaline aqueous liquids such as caustic potash and caustic soda, or #i (and) hydrogen peroxide,
There are oxidizing agents such as sodium hypochlorite. Note that these aqueous liquids can contain an appropriate amount of a solvent such as methanol.

In particular, hydrofluoric acid with a concentration of 10 to 50% by weight, hydrogen peroxide solution of 5 to 50% by weight, and 5 to 70% by weight used in semiconductor manufacturing processes.
An aqueous solution of nitric acid at % by weight, sulfuric acid at 5-98% by weight, alone or in combination, is applied.

The removable suspended fine particles in the aqueous liquid include inorganic fine particles,
The suspension contains 10'' to 10 particles of oil-based particles, polymeric substance particles, etc. with a particle size of 0.2 μ or more/aqueous liquid α.

Now, acid or alkali or (and) III! In order to remove suspended fine particles in an aqueous liquid containing a curing agent using a hollow fiber made of a porous membrane according to the present invention, either total filtration or partial filtration in which a part of the influent is discharged or recycled. method can be applied.

In general, partial filtration is preferable for long-term use or when there are many suspended fine particles.

Furthermore, the hollow fiber has an inner diameter of 0.05 to 5cm and a membrane thickness of 0.03cm.
There are applications in which partial circulation filtration using such hollow fibers can maximize its effectiveness.

In the present invention, the hollow fiber made of such a porous membrane is
Unlike other pleated, snot-like membranes, the membrane itself is the support, so the membrane is highly purified before and after use, keeping the purification of aqueous liquids at 1 ft high and maintaining it during operation. It is also possible to perform flash clean operations and the like.

Therefore, the method of the present invention is particularly suitable for purifying chemicals used in the semiconductor industry, and is capable of converting suspended fine particles contained in a raw aqueous liquid into fine particles with a particle size of 0.2 μ or more per aqueous liquid α.
It is possible to remove and purify from 03 to 106 pieces to 2X10'' pieces/CC or less.

Example 1 A 40% by weight aqueous solution of sulfuric acid containing 400 ppm of silicon oxide was filtered through the following three types of microporous membranes, and the trapping efficiency of the fine particles contained therein and the total filtration amount were measured. The results are shown below.

Membrane A (Example 1) Has a porosity of 60X, an average pore size of 0.20μ, and an inner diameter of 1.5
■Polyethylene hollow fiber B membrane with a membrane thickness of 0.5■ (Comparative Example 1) Cellulose acetate flat membrane with an average pore i of 0.20μ (membrane thickness 150μ) 0 membrane (Comparative Example 2) with an average pore diameter of 0.22μ (4) Examples @) Comparative Example 1 (C) Comparative Example 2 Total filtration amount 4
2) 100 20 10 Note) Bottle 1) Example membrane Relative value when 1kloO First, the stock solution and filtrate were diluted with pure water, and the imitated particles were captured on a microfilter membrane having a concentration of 110.2μ, and then placed on the membrane. Captured light particles#
! 1' was measured using a direct microscope method, and the capture efficiency after filtration was determined from the difference in the number of particles between the stock solution and the filtrate, and the value of the example membrane was 1k.
It was calculated relatively as loo.

Note) Bottle 2) f! of the example membrane! Relative value when the filtration rate is 100 g, given the same flow rate per membrane area, the maximum differential pressure for the filtration is 3 K
q/lx'' was measured, and that of the example membrane was set as 100.

In addition, the surface of Comparative Example Membrane 2 was wetted with isoglobil alcohol before using the aqueous liquid, and then used.

Example 2 35 parts by weight of dibutyl phthalate, 30 parts by weight of silicic anhydride,
A mixture containing 30 parts by weight of polypropylene was extruded into hollow fibers, and then dibutyl phthalate was added to E:IC:I/
This bale was further extracted with silicic anhydride T-40% caustic soda, and was made of a microporous membrane with a pore size of 0.10μ and a porosity of 60%, with an inner diameter of 1.2 am, a membrane thickness of 0.25μ, and a membrane area of o. , s m'' hollow fiber continuous porous filter was obtained.

This filter is presoaked with methanol and then with water to substantially remove the methanol.

On the other hand, for comparison, a commercially available pleated filter (Millibore, Fluoroguard, nominal pore size 0.22μ, membrane area o,
I prepared a smr.

These two types of filters were installed in a separate tank Km attached to the etching treatment tank, and the etching solution was passed through the filter continuously through a pump.

At this time, the example filter had a linear velocity of 0.5'm/sec.
The filtrate is passed through the inside of the hollow fiber at a speed of
This was combined with the liquid extracted from the treatment tank and subjected to circulation filtration.

On the other hand, separately, the filter of the comparative example was subjected to total filtration so that the initial filtration was equal to that of the example filter.
Make sure to return the filtrate to its original state.

0 at the point where it enters the filter population from the etching treatment tank.
The initial number of suspended fine particles of 2 μ or more was 5×10′ particles/piece.

When silicone urethane was actually photoetched for about 12 hours and the filtration rates of Examples and Comparative Examples immediately before and after the start of treatment were added, the following results were obtained.

Example filter Comparative example filter filtration rate, e/min -m" Start @ after 1015 12 hours later 84 As shown above, the example filter showed substantially less decrease in filtration rate after 12 hours, and 1 In contrast, the comparative example had poor filtration speed and poor particle trapping efficiency.

Example 3 Using a process similar to Example 2, a hollow fiber with an inner diameter of 0.8 mm, a membrane thickness of 0.30 mm, and a membrane area of o, sm'' was prepared using a microporous membrane having a pore size of 0.25 μ and a porosity of 65%. A polyethylene continuous porous filter was obtained.

Using this filter, the filtration purity of an aqueous solution containing suspended fine particles containing the following chemicals was measured, and the results shown below were obtained.

For comparison, a pleated filter made of polypropylene flat membrane (trade name: HDO-BN, pore size: 0.22μ,
(manufactured by Ball Co.) was also used.

30% hydrogen peroxide solution 10” 50
30045% hydrofluoric acid 2X10”
35 40060% Nitric acid 2X
10' 150 70080% Sulfuric acid 2X10' 170 600 Example 4 A process similar to Example 2 was used to reduce the pore size to 0.30.
μ, microporous membrane with porosity of 60%, io, 6
A microporous hollow fiber (sample A) of ethylene-47-modified ethylene copolymer having a film thickness of 0.40 cm was obtained.

Similarly, polyvinylidene fluoride porous hollow fibers (sample B) having the same size and pore diameter and a porosity of 58% were obtained.

When the sample of Example 2 was filtered through a 98% sulfuric acid solution (fine particles of 0.2μ or more xo'l1m/CC), the filtration characteristics shown above were obtained.

Example sample (4) Example sample 0) Filtration rate (J3/
hr -m”-aim) 3,000
2,500 The above results show that the hollow fiber membrane of this example is extremely effective even for the sulfuric acid liquid.

This hollow fiber membrane could be easily washed after use, and the filtration rate returned to its original value after washing with extremely clean water.

Patent applicant Asahi Kasei Kogyo Co., Ltd. Procedural amendment (method) % formula % L Case display Showa! 2 year patent application No. 4tjdtt
No. 2 Title of the invention: A method for removing suspended fine particles from an aqueous liquid containing an acid, an alkali, or an oxidizing agent.

a Relationship with the case of the person making the amendment Patent applicant 4 Date of amendment order June 7, 1939 (Shipping date j7.1, 2) "Name" Column 6 Contents of Amendment Contents of Amendment (1) Amend the application as shown in the attached sheet.

(2) Amend the title of the invention in the description as shown.

[Method for removing suspended particles from aqueous liquids containing acids, alkalis, or oxidizing agents”

Claims (1)

[Scope of Claims] 1. Suspended fine particles in an aqueous liquid containing an acid or alkali or/and an oxidizing agent have a porosity of 15 to 90% and an average pore size of 0.
．． Inner diameter 0.05~ made of microporous membrane with O1~5μ
Removal of suspended fine particles from an aqueous liquid containing an acid or alkali or (and) an oxidizing agent, characterized by removal using a polyolefin or polyvinylidene fluoride resin hollow system with a film thickness of 5 m and a film thickness of 0.03 to 2. Method 2: Method λ according to claim 1, wherein the oxidizing agent of the aqueous liquid is hydrogen peroxide, nitric acid, or sulfuric acid. The method according to claim 1, which is a suspension containing a palpitation fluid α.