JP2003144822A - Filter material for high performance air filter which is fire-resistant and reducible in volume by incineration and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high performance filter material which does not contain halogen and is made entirely of glass fiber and a filter material for a high performance air filter which is fire-resistant and is reducible in volume by incineration. SOLUTION: The filter material for the air filter is constituted so as to compound a base material by blending glass fiber of average fiber diameter <=0.65 μm or a glass fiber mixture comprising mainly the same of 10-50 wt.% with at least one kind of organic heat resistant fiber having a melting point/ decomposition point of >=280 deg.C and an LOI value (limit oxygen index) of >=30 and not containing halogen or an organic fiber mixture comprising mainly the same of 50-90 wt.% admix the base material of 100 wt.% with a binder component of 1-10 wt.% and have the fire resistance satisfying the class 3 in the method described in L-1091 A-1 method in JIS fire resistance test method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to semiconductors, liquid crystals, clean rooms related to the bio / food industry, local equipment, and RI (radio isotope) related nuclear power generation facilities, hospital facilities, etc. The present invention relates to a high performance air filter medium.

[0002]

2. Description of the Related Art Conventionally, as a high performance air filter medium,
Glass fiber as the main raw material is widely used. As a high-performance air filter media, particle size 0.3 μm DOP
There are a HEPA filter medium that collects 99.97% or more of (dioctyl phthalate) particles and a ULPA filter medium that collects 0.1 μm particle diameter DOP particles and has a trapping efficiency of HEPA or higher. However, the used filter media made of glass fiber cannot be reused and cannot be incinerated, so it is discarded as industrial waste. In particular, used filter media used in RI facilities becomes a radioactive waste, which is a major environmental problem.

For this reason, a volume-reducing high-performance air filter medium has been developed in recent years in which flammable organic fibers are mixed with glass fibers to reduce the volume by a combustion process. However, when a flame ignites the filter medium in an accident such as a fire. Since it does not have flame retardancy like that of all-glass fiber, there is a demand for a high-efficiency air-filter filter material that can be incinerated and reduced in volume, but that is as flame-retardant as that of all-glass fiber. .

As a method of imparting flame retardancy, Japanese Patent Publication No. 63-5
As shown by 6806, a method of applying a flame retardant to a filter medium has been proposed. However, in order to have good flame retardancy with this method, a considerable amount of flame retardant must be used, and the produced filter medium is clogged with the flame retardant in the voids of the constituent fibers, resulting in air filter pressure. There is a problem that a high-performance filter medium cannot be produced due to an increase in loss and a decrease in collection efficiency.

Further, as shown in Japanese Utility Model Publication No. 22417/1994, there is an example in which a glass fiber is mixed with a self-extinguishing organic fiber and bonded with an acrylic resin binder, but the binder is selectively concentrated on the glass fiber. There is a problem that a film is formed by this, and this lowers the flame retardancy.

In order to improve this, the present inventors proposed a method in Japanese Patent Laid-Open No. 10-180020 in which glass fibers are mixed with self-extinguishing organic fibers and the fibers are bonded with a fibrous binder. At the same time, the filter performance (PF
The value) was improved and the filter medium was improved in low pressure loss and high efficiency.

These self-extinguishing organic fibers are, for example, vinyl chloride fiber, modacrylic fiber, polyclar fiber, flame-retardant vinylon fiber, PVC acetate fiber in which halogen is introduced in the molecular chain, or a phosphorus compound is kneaded into the resin or the molecular chain is incorporated. The flame-retardant polyester fiber, the flame-retardant acrylic fiber, the flame-retardant polynosic fiber, etc. introduced in the above, and the flame-retardant fiber obtained by kneading an inorganic flame retardant into a resin.

However, in recent years, chlorine components and halogen-based compounds may generate toxic dioxin when incinerated, so that market demand for dehalogenation has been increasing, and halogen-based self-extinguishing organic fibers are used. It became necessary to make filter media without doing so.

Further, phosphorus-based self-extinguishing organic fibers and inorganic self-extinguishing organic fibers have weaker flame retardancy than halogen-based ones,
In particular, phosphorus-based compounds may impair the formation of a carbonized layer during combustion due to the incorporation of glass fibers and lose flame retardancy, which is insufficient to satisfy JIS Flame Retardant Test Method L-1091 A-1 Method Category 3 Met.

[0010]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high-performance filter medium made of all-glass fiber which does not contain halogen and is as flame-retardant as possible, and a filter medium for incineration and volume reduction, which can be reduced in volume, and its production. Is to provide a method.

[0011]

The object of the present invention is to contain 10 to 50% by weight of a glass fiber having an average fiber diameter of 0.65 μm or less or a glass fiber mixture mainly containing the glass fiber, which does not contain halogen, and has a melting point and a decomposition point of 280 ° C. At least one kind of organic heat-resistant fiber having a higher LOI value (limit oxygen index) of 30 or more, or an organic fiber mixture mainly composed of the same 50 to 90
1 wt% to 10 wt% of the binder is added to 100 wt% of the base material, and JIS
Flame retardant test method L-1091 A-1 having a flame retardance satisfying Category 3 by the method described in the method, characterized by the incineration and volumetric performance filter material having the above flame retardancy. It is solved by the manufacturing method.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The glass fiber used in the present invention is a wool-like glass fiber produced by a flame drawing method or a rotary method, and keeps the pressure loss of a filter medium at a predetermined value to obtain an appropriate collection efficiency. It is an essential ingredient for The finer the fiber diameter, the higher the collection efficiency. Therefore, in order to obtain a high-performance filter medium, it is necessary to add ultrafine glass fibers having an average fiber diameter of 0.65 μm or less. However, if the fiber diameter becomes thin, the pressure loss may increase too much, so that the fiber diameter should be selected within this range. In addition, you may blend and mix several types of fiber diameter.

It is suitable that the compounding ratio of the glass fiber is 10 to 50% by weight. If it is more than 50% by weight, the purpose of incineration and volume reduction is lost, and if it is less than 10% by weight, the absolute amount of glass fiber is insufficient. It will deteriorate the collection efficiency.

Further, the organic heat-resistant fiber has a flame-retardant structure (heat-resistant structure) from the molecular structure, and when incinerated, it is only carbonized and does not burn by raising a flame at all. The combustion behavior is different from that of the self-extinguishing fiber having the. By the way, while many self-extinguishing fibers have a melting point / decomposition point of 160 to 280 ° C., organic heat-resistant fibers have a thermal property of higher than 280 ° C. or not melting at all. Also, the LOI value (limit oxygen index) has a high value of 30 or more.

These characteristics of the heat-resistant fiber make it possible for the filter medium to have the severe flame retardancy of JIS flame retardant test method L-1091 A-1 method category 3. Further, even if another material of glass fiber is blended, the self-extinguishing property is not impaired unlike the phosphorus-based self-extinguishing fiber.

Examples of the organic heat-resistant fiber include novoloid fiber, polyamideimide fiber, polyphenylene sulfide fiber, polybenzimidazole fiber, polyparaphenylene benzobisoxazole fiber, meta-aramid fiber, and carbon fiber. Although not limited, it is desirable that the dispersibility at the time of slurry and the filter sheet have a good skin from the viewpoint of production, and if the raw material is poor, it is necessary to add a dispersant, a sticking agent and other papermaking chemicals. Above all, novoloid fibers are more preferable in this respect and cost.

Further, if the flame-retardant classification 3 and other filter media performance can be secured, a part of the compound of the organic heat-resistant fiber is
It may be replaced with flammable fibers such as polyester fibers, acrylic fibers, vinylon fibers, polyethylene fibers, polypropylene fibers and rayon fibers.

Regarding the flame retardancy of the filter medium, the method described in JIS L-1091 A-1 method for flame retardancy was used to heat the filter medium for 1 minute with a micro burner from below with the surface of the filter inclined at 45 °. Carbonization area after 30cm ² or less, carbonization distance 2
If it satisfies 0 cm or less, afterflame time of 3 seconds or less, and dust time of 5 seconds or less (Category 3), it can be regarded as flame retardant comparable to an all-glass fiber high-performance air filter medium.

Next, since the glass fiber and the organic heat-resistant fiber do not have adhesiveness themselves, a binder is added to maintain the strength of the filter medium. As the binder, a liquid binder such as an acrylic resin, a urethane resin, a vinyl acetate resin, a styrene-butadiene resin, an epoxy resin, a polyvinyl alcohol resin, or the following fibrous binder, that is, a wet heat fusion type PVA fiber Examples thereof include binders and core-sheath fibers using low melting point PE, modified PP, modified polyester and the like in the sheath portion, and these may be used alone or in combination.

Conventionally, when a liquid binder is used for a filter material that can be incinerated and reduced in volume, as described above, the binder selectively concentrates on the glass fiber to form a film, which causes a problem of reducing flame retardancy. However, since the organic heat resistant fiber has extremely high flame retardancy, such a problem does not occur.

Further, the fibrous binder does not form a film like the liquid binder and concentrates on the glass fibers to form a point bond between the main fibers. Since the binder film does not cause an increase in pressure loss and a decrease in collection efficiency, it is desirable for producing a filter medium having higher filtration performance.

The rate of application of the binder to the substrate is 1 to
10% by weight is desirable, and if less than 1% by weight, the strength of the filtering material that can withstand filtering and practical use does not appear, and if it is 10% by weight or more, the binder causes clogging of the filtering material and pressure loss increases, resulting in poor filtering performance. Resulting in. Further, if the amount of the combustible binder is large, the flame retardancy is deteriorated.
The filter material for an air filter of the present invention is manufactured as follows. First, raw material fibers mainly composed of glass fibers are disintegrated and dispersed in water using a pulper or the like to obtain a slurry. Here, in order to improve the dispersibility of the glass fiber, it is preferable to add sulfuric acid or hydrochloric acid to adjust the pH to about 2 to 4, or to add a dispersant under neutral conditions. The fibrous binder needs to be used in a so-called internal addition method in which it is mixed with the raw material slurry in this disaggregation / dispersion step. By this method, the fibrous binder can be uniformly dispersed and spot-bonded over the entire raw material, so that its ability in terms of filtration performance can be exhibited. The slurry is paper-made in a paper machine to form a wet paper. The liquid binder is the above-mentioned internal addition method, or a method of adding a binder to this sheet after forming a wet paper, or a method of forming a wet paper and then adding a binder to a once dried sheet (above, external addition method) , Etc., and can be selected according to the specifications of the manufacturing apparatus. Examples of the external addition method include a method of dipping and applying the binder liquid in the sheet, a method of applying the binder liquid by coating or spraying on the sheet, and the like. Further, if necessary, in order to impart water repellency to the filter medium, a water repellent such as a fluorine-based, silicon-based, or wax-based water repellent may be added by an external addition method. After the above treatment, the sheet is dried using a hot air dryer, a rotary dryer or the like to obtain a filter medium. Here, in order to exhibit sufficient strength of the filter medium, it is desirable that the drying temperature is 110 ° C. or higher.

[0023]

EXAMPLES Next, the present invention will be described more specifically by way of Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 7% by weight of ultrafine glass fibers having an average fiber diameter of 0.32 μm, 23% by weight of ultrafine glass fibers having an average fiber diameter of 0.5 μm, a fiber diameter of 2 d (denier), and a novoloid fiber having a fiber length of 6 mm ( Kynol: Gunei Chemical Industry Co., Ltd., melting point / decomposition point 350 ° C., LOI value 30 to 3
4) 70% by weight is blended, concentration 0.5%, sulfuric acid pH
Pulper disaggregation was performed under 3.0 conditions. Then, papermaking was performed using a hand-making cylinder to obtain a wet paper web. Acrylic latex binder (Bond Coat A, Dainippon Ink and Chemicals, Inc.)
N-155) as a solid content based on 100% by weight of the base material.
% By weight, and then dried by a dryer at 130 ° C. to obtain a filter medium having a basis weight of 80 g / m ² .

[Example 2] 30% by weight of ultrafine glass fibers having an average fiber diameter of 0.5 μm, novoloid fibers having a fiber diameter of 2 d and a fiber length of 6 mm (Kynol: manufactured by Gunei Chemical Industry Co., Ltd.,
Melting point / decomposition point 350 ° C., LOI value 30 to 34) 70% by weight, fibrous PVA binder (VPB 107-2:
3% by weight of Kuraray Co., Ltd. was added to give a concentration of 0.5.
%, Sulfuric acid acidic pH 3.0 conditions were used for pulper disaggregation. Then, papermaking was performed using a hand-making cylinder to obtain a wet paper web. This wet paper 13
It was dried with a dryer at 0 ° C. to obtain a filter medium having a basis weight of 81 g / m ² .

[Example 3] In Example 2, the wet paper state before drying was impregnated with an aqueous solution of a water repellent (Light Guard FRG-1 manufactured by Kyoeisha Chemical Co., Ltd.) having a solid content concentration of 0.1% by weight. A unit weight of 81 g /
A m ² filter medium was obtained.

Example 4 Polyparaphenylene benzobisoxazole (PBO) fiber having a fiber diameter of 1.5 d and a fiber length of 1 mm instead of the novoloid fiber (Zylon: manufactured by Toyobo Co., Ltd., melting point Decomposition point 650
C., LOI value 68) Example 2 except that 70% by weight was blended
A filter material having a basis weight of 80 g / m ² was obtained in the same manner as in.

Example 5 In Example 2, polyphenylene sulfide (PPS) fiber having a fiber diameter of 1.3d and a fiber length of 6 mm in place of the novoloid fiber (torcon: Toray Industries, Inc., melting point / decomposition point 285 ° C.) , LOI value 34)
A filter material having a basis weight of 81 g / m ² was obtained in the same manner as in Example 2 except that 70% by weight was blended.

[Comparative Example 1] In the raw material formulation of Example 2, except that 5% by weight of ultrafine glass fibers having an average fiber diameter of 0.26 μm and 95% by weight of novoloid fibers were blended with 3% by weight of a fibrous PVA binder. In the same manner as in Example 2, a filter material having a basis weight of 80 g / m ² was obtained.

Comparative Example 2 The weight per unit area was 80 g in the same manner as in Example 2 except that the content of the fibrous PVA binder was changed from 3% by weight to 12% by weight in the raw material formulation of Example 2.
A filter material of / m ² was obtained.

[Comparative Example 3] In Example 2, a halogen-based flame-retardant vinylon fiber (VPX 203: manufactured by Kuraray Co., Ltd.) having a fiber diameter of 2d and a fiber length of 6 mm instead of the novoloid fiber was used.
Melting point / decomposition point 220-230 ° C, LOI value 28-33)
A filter material having a basis weight of 81 g / m ² was obtained in the same manner as in Example 2 except that 70% by weight was blended.

[Comparative Example 4] In Example 2, instead of the novoloid fiber, a phosphorus-based flame-retardant polynosic fiber having a fiber diameter of 1.5 d and a fiber length of 3 mm (Tough van: manufactured by Toho Boshoku Co., Ltd., melting point / decomposition point 260). ~ 300 ° C, LOI value 28 ~ 3
2) A filter material having a basis weight of 80 g / m ² was obtained in the same manner as in Example 2 except that 70% by weight was blended and 3% by weight of the fibrous PVA binder was changed to 8% by weight.

The analysis of Examples and Comparative Examples was performed by the following method. Flame retardance is JIS flame retardant test method L-1091A
-Based on the -1 method test, Category 3 (carbonized area 30 cm ²
In the following, those satisfying the carbonization distance of 20 cm or less, afterflame time of 3 seconds or less, residual dust time of 5 seconds or less) were evaluated as ◯, those not compatible were evaluated as x, and those partially compatible were evaluated as Δ. In the halogen reaction during combustion, it was determined that halogen gas was generated when the universal pH test paper was exposed to the combustion gas when the filter medium was combusted and turned red. The pressure loss was measured by using a manometer to measure the differential pressure when passing through a filter paper having an effective area of 100 cm ^{2 at} a surface wind velocity of 5.3 cm 3 / sec. The DOP collection efficiency is 100c of effective area for the air containing polydisperse DOP particles generated by the Ruskin nozzle.
The DOP collection efficiency when passing through a m ² filter paper at a surface wind velocity of 5.3 cm 3 / sec was measured using a laser particle counter. The target particle size was 0.3 μm. The PF value, which is an index of the filtration performance of the filter medium, was obtained by the following formula from the measurement results of pressure loss and DOP collection efficiency. (The higher the PF value, the higher the collection efficiency at the same pressure loss.) (PF value) = Log ₁₀ {[100- (collection efficiency)] / 1
00} / (pressure loss) × 9.81 × (-100) The tensile strength was measured according to JIS P8113. The combustible material was heated at 925 ± 25 ° C. for 10 minutes in an electric furnace, and the weight difference before and after heating was divided by the weight before heating to obtain a percentage.

[0034]

[Table 1]

[0035]

INDUSTRIAL APPLICABILITY The air filter medium of the present invention has higher flame retardancy than the conventional flame-retardant filter medium using self-extinguishing fiber, and it can greatly reduce halogen gas and dioxins during incineration. It is excellent in that the filter volume can be reduced.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) D21H 13/40 D21H 13/40 F24F 7/00 F24F 7/00 A 7/06 7/06 C G21F 9 / 02 551 G21F 9/02 551E F term (reference) 3L058 BF09 4D019 AA01 BA03 BA13 BA16 BC11 BC12 CB06 CB08 DA03 4L055 AF04 AF21 AF30 AF32 AG71 AH23 AH37 EA04 EA20 FA20 FA30 GA31

Claims (4)

[Claims] 1. A glass fiber having an average fiber diameter of 0.65 μm or less or a glass fiber mixture mainly composed of 10 to 50% by weight does not contain halogen and has a melting point / decomposition point of 280 ° C.
At least one organic heat-resistant fiber having a higher LOI value (limit oxygen index) of 30 or more or 50 to 90% by weight of an organic fiber mixture mainly composed of the same is blended, and the base material 1
A binder content of 1 to 10% by weight is added to 00% by weight, and JIS flame retardant test method L-1091A is used.
A high-performance air filter medium capable of incineration and volume reduction, characterized by having flame retardancy satisfying Category 3 by the method described in Method-1. 2. The high-performance air filter medium capable of incineration and volume reduction according to claim 1, wherein the binder component is a fibrous binder. 3. The high-performance air filter medium capable of incineration and volume reduction according to claim 1 or 2, wherein the organic heat-resistant fiber is a novoloid fiber. 4. The method for producing a filter material for a high-performance air filter capable of incineration and volume reduction, which has flame retardancy according to any one of claims 1 to 3, wherein the fiber is used in a raw material adjusting step before the papermaking step of the raw material fiber. The above-mentioned production method, characterized in that a paper-like binder is added, the paper is made by a wet paper-making method, and then dried.