JPH07194911A - Filter paper and air filter using the same - Google Patents

Abstract

PURPOSE:To provide an air filter which can catch particles and control a boron concentration at 10kg/m<3>. CONSTITUTION:Paper made by a wet process using glass fibers of 0.2-12mum diameter is impregnated with l-23wt.% of paper of a polyhydric alcohol or its derivatives having two or more asymmetric carbons to make filter paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filter paper used for collecting particles and gaseous boron in a gas, and an air filter using the filter paper.

[0002]

2. Description of the Related Art As a conventional air filter, for example, there is one that uses a wet paper made of borosilicate glass fiber and uses a filter paper to which a binder and a water repellent are added, which collects dust particles with high efficiency ( 99.97 0.3 μm particles
% Or more), it is widely used for air purification in clean rooms for manufacturing electronic devices such as LSI.

However, as the degree of integration of electronic devices has improved, as the exposure time of the electronic devices to the air in the clean room becomes longer, the characteristics of the electronic devices deteriorate. One of the causes of this deterioration is the release of boron from the borosilicate glass fiber used in the air filter. That is, most of the air in the clean room is recirculated, and the boron generated from the air filter is gaseous and floats in the clean room, which adheres to the electronic device in the process of manufacturing and deteriorates its characteristics. .

In recent years, a clean room for manufacturing a 1G LSI has been required, and it has been said that it is necessary to control the boron concentration to 10 ng / m ³ or less in this clean room.

[0005]

Therefore, an object of the present invention is to provide a filter medium and an air filter capable of collecting both particles and gaseous boron, and further, to collect particles and a boron concentration of 10 ng. An object of the present invention is to provide an air filter that can suppress the amount to / m ³ .

[0006]

The filter paper and air filter of the present invention are formed by adhering a polyhydric alcohol or a derivative thereof. The amount of the polyhydric alcohol or its derivative impregnated is preferably 0.2 to 23% of the weight of the paper, and the fiber diameter of the filter paper is preferably 0.2 to 12 μm. The alcohol or its derivative is preferably a compound having a hydroxyl group at the cis position.

On the other hand, the filter paper and the air filter of the present invention are produced by a wet method using glass fibers having a fiber diameter of 0.2 to 12 μm, and 1 to 23% of asymmetric carbon of the paper weight is added to the paper. A polyhydric alcohol or a derivative thereof having more than one is impregnated. It is preferable that the steam dryer is manufactured at a drying temperature of 115 ° C. or lower.

[0008]

The present invention operates as follows.

In the filter paper and the air filter, since the polyhydric alcohol or its derivative is impregnated, the impregnated substance and boron are chemically bound, and as a result, the particles are collected. That is, gaseous boron can also be collected.

When the amount of polyhydric alcohol or its derivative impregnated is 0.2 to 23% of the weight of paper,
The saturated adsorption amount of boron is large and an increase in pressure loss as a filter paper can be suppressed.

The above is clear from the following experimental results (Table 1, Table 2, FIG. 2). [Experiment 1 / Boron collection test] The device shown in FIG. 1 (in FIG. 1,
Reference numerals 10a and 10b are flowmeters, reference numeral 11 is a membrane filter, reference numeral 12 is a boric acid aqueous solution, reference numeral 13 is a membrane filter, reference numeral 14 is a sample filter paper, and 15a, 15b, 1
5c and 15d are pure water, and 16a and 16b are flowmeters.)
Thus, 3.5 × 10 ³ ng of boron per 1 cm ^{2 of} filter paper (corresponding to 2.5 × 10 ⁴ hours of use in cleanroom) was loaded, and the boron collection rates of the filter media were compared.
The results are shown in Table 1.

[0012] It can be seen from Table 1 above that regardless of the type of fiber, the one with N-methyl-D-glucamine impregnated has a very excellent boron collection rate as compared with the one without N-methyl-D-glucamine. [Experiment 2 / Boron collection test and filter paper pressure loss test when the amount of impregnation was changed] First, N- for borosilicate fiber
The amount of methyl-D-glucamine impregnated was changed, and changes in the boron collection rate and the pressure loss of the filter paper (ventilation speed of 5.3 cm / s) were compared in the same device as in Experiment 1. The result is shown in FIG.

From FIG. 2, in order to increase the collection rate of boron (collection rate of 80% or more) and suppress the increase of pressure loss of the filter paper (pressure loss increase rate of 25% or less), N -
Methyl-D-glucamine impregnation amount per paper weight is 0.2
It can be seen that -23% is preferable.

In addition, the polyhydric alcohol or its derivative is N-
When a substance other than methyl-D-glucamine is used and the impregnation amount is 7% of the weight of the filter paper, the boron collection rate and the pressure loss of the filter paper are as shown in Table 2 below. The ventilation speed used for measuring the pressure loss of the filter paper is 5.3 cm / s. From Table 2 above, even if it is other than N-methyl-D-glucamine, if the polyhydric alcohol or its derivative is impregnated, the boron collection rate is excellent (when sucrose or D-glucosamine hydrochloride is impregnated. Although the collection rate has not reached 80%, it is clear that it has the effect compared to the case where nothing is attached at all), and it can be seen that there is almost no increase in the pressure loss of the filter paper.

The actual ventilation speed is about 1.0 cm / s, which has almost no effect on the increase in the pressure loss of the filter paper. [Experiment 3 / Boron generation test from filter paper when the amount of impregnation was changed] The amount of L-tartaric acid impregnated on the borosilicate fiber was changed, and the apparatus shown in FIG. 3 (reference numeral 20 was a test filter paper, reference numeral 2 was used).
1a and 21b are pure water bubblers, reference numeral 22 is a flow meter, and reference numeral 23 is an air pump, and a boron generation amount test (conditions: temperature 22 to 24 ° C., humidity 35 to 40% RH) was performed. The result is shown in FIG.

From FIG. 4, in order to keep the amount of boron generated low, the amount of L-tartaric acid impregnated per 1% by weight of paper is 1%.
It can be seen that the above (the amount of generated boron is 10 ng / m ³ or less) is preferable.

Next, a borosilicate fiber was impregnated with polyhydric alcohol or its derivative in an amount of 5% of the weight of the filter paper, and the apparatus shown in FIG. 3 was used to compare the amount of boron generated from each filter paper under test (condition: temperature. 22-24 ° C, Humidity 35-40% R
H) was performed. The results are shown in Table 3. From Table 3 above, the amount of boron generated can be suppressed to 1/7 or less by impregnating the polyhydric alcohol or its derivative.

Further, in the case of one having two or more asymmetric carbon atoms such as L-tartaric acid or D-sorbitol, the amount of boron generated is 1 /
It is clear that it can be suppressed to 30 or less (10 ng / m ³ or less). It is considered that this is because a structure having two or more asymmetric carbons has a higher probability of forming a stable bond with boron. [Experiment 4 / Test for Examining Relationship between Drying Method of Filter Paper and Boron Generation Amount] After impregnating the filter paper after papermaking with an emulsion of (binder) + (water repellent) + (L-tartaric acid),
The filter paper was dried with an air dryer and a steam dryer, and a boron generation test was conducted with the apparatus shown in FIG. 3. The results shown in Table 4 below were obtained.

[0019] [Experiment 5 / Test for examining the relationship between the drying temperature of the filter paper and the amount of generated boron] The filter paper after papermaking is immersed in an emulsion of (binder) + (water repellent) + (L-tartaric acid), and a steam dryer is used. It was dried by changing the temperature. The amount of boron generated from this filter paper was measured by the device shown in FIG. The result is shown in FIG.

It can be seen from FIG. 5 that a lower drying temperature is preferable. This is because the steam dryer wraps the filter paper around the drum to dry it, so that it is said that the binder is transferred along with the steam generated during drying, and the attached chemicals are transferred, resulting in uneven distribution of the chemicals.
It is considered that boron was easily generated. Therefore, it is understood that the temperature of the steam dryer is preferably 115 ° C. or lower in order to reduce the amount of generated boron (10 ng / m ³ or lower).

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described below with reference to the drawings shown as embodiments. (Example 1) In the air filter of this example, a filter paper folded in a zigzag shape was attached to a frame of an aluminum mold member in an airtight state on the outer periphery, and the filter paper had a small diameter made of borosilicate glass fiber as a base material. Fiber (Fiber diameter distribution 0.
2 to 2.65 μm, average diameter 0.85 μm) and a small amount of large diameter fibers (E glass fiber: silicon oxide 55%, boron oxide 8%, calcium oxide 17%) for reinforcing the mutual connection of the small diameter fibers. , And other fiber diameter distributions of 8 to 24 μm) and 7% of the weight of paper attached to them, N-methyl-D-glucamine (chemical formula CH ₃ NHCH ₂ (HCOH) ₄ CH ₂ OH).

This air filter can be manufactured by the following operations. First, as the basic material, fine fibers made of borosilicate glass fibers (fiber diameter distribution 0.2 to 2.65 μm, average diameter 0.
85 μm) and a small amount of large-diameter fibers (E glass fiber: 55% silicon oxide, 8% boron oxide, 17% calcium oxide, other fiber diameter distribution 8-24 μm) for reinforcing the mutual connection of the small-diameter fibers. Is dispersed in water adjusted to pH 2 with a sulfuric acid solution, and papermaking is performed.

After the above-mentioned papermaking, 2% of acrylic resin per weight of solution as a binder, 0.3% of fluororesin per weight of solution as a water repellent, and 1% of N- per weight of solution.
A filter paper is manufactured by immersing in an emulsion to which methyl-D-glucamine is added, forming a sheet and drying.

Then, the filter paper is folded in a zigzag shape,
The air filter (hereinafter, the symbol of the air filter will be referred to as AF) can be manufactured by hermetically attaching it to the frame of the aluminum mold member with the urethane resin.

Here, the boron collection rate was measured in an actual clean room CR using the air filter AF manufactured as described above. Clean room C in Figure 6
1 shows R and boron concentration measuring devices 5, 5 '.

In the clean room CR, as shown in FIG. 6, the ceiling is made up of a large number of ULPA filters 3a, and the floor is made up of a floor plate 4a having air passage holes. As shown in the figure, an air supply chamber 3 is provided above the ULPA filter 3a, an air discharge chamber 4 is provided below the floor plate 4a, and the air supply chamber 3 and the air discharge chamber 4 are provided. They are connected to each other by piping to circulate the air in the clean room CR and to discharge a part of the circulated air and take in the outside air during the circulation of the air.

As shown in FIG. 6, the boron concentration measuring device 5 measures the boron concentration of the air immediately after passing through the air filter AF, and the pure water bubblers 51, 51 and the air passing through the air filter AF are measured. The pure water bubbler 51,
It is composed of an air pump 52 that sucks through 51, and a flow meter 53 that adjusts the amount of air sucked by the air pump 52. In the vicinity of the air filter AF, a fan 50 for forcibly passing the air in the clean room CR is provided.

As shown in FIG. 6, the boron concentration measuring device 5'measures the boron concentration of the air in the clean room CR, and its constitution is the above boron concentration measuring device 5 '.
Same as with.

The boron concentration measurement values obtained by these boron concentration measuring devices 5 and 5'are obtained by measuring the concentration of boron in the recovered liquid of the pure water bubbler 51 with an ICP-MS (high frequency inductively coupled plasma mass spectrometer). The boron collection rate of the air filter AF was obtained from the measured values of the boron concentration by these concentration measuring devices 5 and 5 ′. Further, similarly to the above, an air filter AF using a filter paper made of borosilicate fiber not impregnated with N-methyl-D-glucamine
Was also manufactured and the collection rate of boron was measured. Then, the air in the clean room was continuously blown into each air filter AF for two months, and then the boron collection rates of both air filters AF were measured again. The results are shown in FIG.

On the other hand, the same test as above was carried out on a filter paper consisting of quartz fiber impregnated with N-methyl-D-glucamine and a filter paper consisting only of quartz fiber not impregnated with N-methyl-D-glucamine. . The result is shown in FIG. [Regarding Embodiment of N-Methyl-D-glucamine Impregnation Treatment Method] N-methyl-D-glucamine impregnation treatment is carried out as follows.
Can be done by ． (Binder) + (Water repellent) + on the filter paper after paper making
Impregnate with an emulsion of (N-methyl-D-glucamine) by spraying or dipping. ． The filter paper after papermaking is impregnated with a binder, and then the filter paper is impregnated with a solution of a water repellent and N-methyl-D-glucamine by spraying or dipping. ． (Binder) + (N-methyl-D- on the filter paper after paper making
Glucamine) emulsion is impregnated by spraying or dipping, and filter paper is impregnated by solution spraying or dipping of water repellent.

[0031] From Table 5, N-methyl-D-glucamine was impregnated by Method A,
It is preferable to carry out at the same time as the binder as in B and C or in a step after the addition of the binder. After impregnating the filter paper after paper making with the N-methyl-D-glucamine solution by spraying or dipping as in Method D, It was found that it is difficult to obtain a high effect when the filter paper is impregnated with the emulsion of (, binder) + (water repellent) by spraying or dipping.

Therefore, methods B and C can be adopted instead of the attachment method of this embodiment. (Example 2) This example is a filter paper impregnated with L-tartaric acid, and the small-diameter fiber and the large-diameter fiber constituting the filter paper are the same as those in the above-mentioned Example 1. The method for producing the filter paper is almost the same as in Example 1, and the filter paper after papermaking is impregnated with an emulsion of (binder) + (water repellent) + (L-tartaric acid) and then steam dryer (115 ° C.). × 6
min) and dried.

When the amount of boron generated from this filter paper was measured by the apparatus shown in FIG. 3, it was 10 ng / m ³ as apparent from FIG. 5 shown in the column of action. That is, when an air filter using this filter paper is adopted, it is possible to create a clean room (boron concentration of 10 ng / m ³ or less per 1 m ^{3 of} air) for manufacturing 1G LSI,
By setting the temperature of the steam dryer to less than 115 ° C, it is possible to create a clean room having a lower boron concentration.

The filter paper having D-sorbitol impregnated also exhibits substantially the same effect as that of the second embodiment as described in the section of action.

Further, a polyhydric alcohol having 1 to 23% of asymmetric carbon atoms of 1 to 23% of the paper weight or a polyhydric alcohol thereof prepared by a wet method using glass fibers having a fiber diameter of 0.2 to 12 μm. If the derivative is attached, this Example 2
The same effect as is obtained.

Further, although the steam dryer is used for drying the filter paper in the second embodiment, the present invention is not limited to this, and an air dryer can also be used.

[0037]

The present invention having the above-mentioned structure has the following effects.

From the contents described in the operation, a filter medium and an air filter capable of collecting both particles and gaseous boron can be provided.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus used for evaluating a boron collection rate.

FIG. 2 is a graph showing changes in boron collection rate and pressure loss of filter paper when the amount of N-methyl-D-glucamine impregnated is changed.

FIG. 3 is a conceptual diagram of an apparatus used for evaluating the amount of boron generated from a test filter.

FIG. 4 is a graph showing the relationship between the amount of L-tartaric acid attached to a filter paper and the amount of boron generated per weight of paper.

FIG. 5 is a graph showing the relationship between the drying temperature of filter paper and the amount of boron generated.

FIG. 6 is a conceptual diagram of an apparatus used for evaluating the boron collection rate of the air filter of the present invention.

FIG. 7 is a graph showing changes in the boron collection rate of an air filter made of borosilicate fiber impregnated with N-methyl-D-glucamine and an air filter made of only borosilicate fiber, depending on the ventilation period.

FIG. 8 is a graph showing a change in a boron collection rate depending on a ventilation period in an air filter made of quartz fiber impregnated with N-methyl-D-glucamine and an air filter made of only quartz fiber.

[Explanation of symbols]

 3 Air Supply Chamber 3a ULPA Filter 4 Air Discharge Chamber 4a Floor Board Material 5 Boron Concentration Measuring Device 5'Boron Concentration Measuring Device 50 Fan 51 Pure Water Bubbler 52 Air Pump 53 Flow Meter

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B01D 53/46

Claims (7)

[Claims] 1. A filter paper comprising a polyhydric alcohol or a derivative thereof attached thereto. 2. A filter paper comprising a polyhydric alcohol or a derivative thereof in an amount of 0.2 to 23% by weight of the paper. 3. A paper made by a wet method using glass fibers having a fiber diameter of 0.2 to 12 μm, and a paper weight of 0.
A filter paper characterized by being impregnated with 2 to 23% of a polyhydric alcohol or a derivative thereof. 4. The filter paper according to claim 1, wherein the polyhydric alcohol or its derivative is a compound having a hydroxyl group at the cis position. 5. A paper made by a wet method using glass fibers having a fiber diameter of 0.2 to 12 μm, wherein
A filter paper characterized by being impregnated with a polyhydric alcohol having 23% or more of two or more asymmetric carbon atoms or a derivative thereof. 6. The drying temperature of the steam dryer is set to 115.
6. The manufacturing method according to claim 1, wherein the temperature is lower than or equal to ℃.
The filter paper described in any of 1. 7. An air filter comprising the filter paper according to any one of claims 1 to 6 as a constituent member.