JPS63236512A - Air filter filtering medium - Google Patents

Abstract

PURPOSE:To prepare a filtering medium of high dust collecting rate and volume- reducible in combustion by forming a mixture consisting of 2-50wt.% organic fibers of 1mum fiber diameter or less and inorganic fibers of 5mum or more fiber diameter for the remaining part into a sheet. CONSTITUTION:An air filter medium is prepared by forming a fiber mixture consisting of 2-50wt.% organic fibers of 1mum fiber diameter or less and 50-98wt.% organic fibers of fiber diameter 5mum or more into a sheet. For the preparation of organic fibers of 1mum fiber diameter or less, extremely superfine fibers of organic synthetic high molecules, micro-fibrillated substances, whiskers and the like are used. As for organic fibers of 5mum fiber diameter or more, synthetic fibers, pulps and the like, preferably of 20mum fiber diameter or less, are used. In case of fibers originated from synthetic high molecules, fibers not containing inorganic pigments or the like should be used for the sake of volume reduction at the time of incineration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-performance filter material for efficiently removing particulates contained in gas and obtaining clean gas.

[Conventional technology and its problems]

Traditionally, paper filters have been used to remove fine dust from the air. Use in this case! The finer the IIi fibers, the greater the particle capture rate, but also the greater the ventilation resistance.

As a filter material for removing fine particles, it is possible to manufacture a material with a small diameter, and it is relatively rigid, so although it can improve the trapping performance, it has a high airflow resistance (because it is difficult to use glass or fiber). However, glass microfibers contain a small amount of microparticles as a by-product during production, and during the production and use of filter media, these microparticles are transferred to the permeate side. It has the disadvantage of falling off.Also, when used to remove dust containing radioactive substances, which is one of the applications of air filtration, the filter material that adsorbs these matsubara is burned to reduce its capacity and disposed of. However, there is a problem in that this volume reduction cannot be achieved with glass fiber.

[Means for solving problems]

In recent years, it has become possible to obtain organic fibers with extremely small diameters, but the inventors were able to achieve a high dust capture rate and The present invention was achieved by successfully obtaining a filter material that has low ventilation resistance and whose volume can be reduced by combustion.

[Structure of the invention]

That is, the present invention uses 2 to 50 organic fibers with a fiber diameter of 1 μm or less.
The present invention relates to an air filter filtration material formed by sheeting a fiber mixture consisting of 50 to 98% by weight of organic fibers having a fiber diameter of 5 μm or more.

The organic fibers having a fiber diameter of 1 μm or less used in the present invention may be selected from among ultrafine fibers of organic synthetic polymers, microfibrillated products, whiskers, and the like.

The manufacturing method is as follows: (a) Manufacture and split splittable composite fibers (1) Spun from solution under shearing force (c) Flush the solution from the high pressure side to the low pressure side and then beat it (2) When the fibers are passed from the high-pressure side to the low-pressure side, they collide with the wall of the vessel and are repeatedly fibrillated. Can be done.

The organic fibers having a diameter of 1 μm or less are preferably as rigid as possible, and fibers made of materials collectively referred to as rigid and straight chain synthetic polymers are particularly suitable. Rigid and linear synthetic polymers are polymers with a long chain length (long persistence length) that maintains a linear shape in solution of 50 Å or more, such as poly (P-phenylene terephthalamide), poly (P-benzamide), etc.
, Ho! J=(P-phenylenebenzobisthiazole),
poly (P-)unisine benzobisoxazole), poly (amide hydrazide), polyhydrazide, poly (
P-phenylene terephthalamide-3,4-diphenyl ether terephthalamide). In particular, these rigid and linear synthetic polymers can be spun into fibers and then microfibrillated into fibrils having a diameter of substantially 1 μm or less using the method (d) above. In this way, fibers spun using normal methods can be used.
Among the above methods, method (d) is economically advantageous.

The organic fibers having a fiber diameter of 5 μm or more used in the present invention include synthetic fibers such as polyolefin, polyamide, and polyester, as well as pulp, lint, lint, and derivatives thereof. In air filters, the smaller the fiber diameter, the better the dust capture rate, so even for fibers with a diameter of 5 μm or more, the diameter is preferably about 20 μm or less. Fibers with a diameter of 5 μm or more and fibers with a diameter of 1 μm
The following fibers can be mixed and dispersed in water to form a slurry, and formed into a sheet by a papermaking method in which water is separated on a wire mesh to form a filter medium.

Unless the fibers with a fiber diameter of 5 μm or more are pulp, linter, or lint, the strength of the paper produced is not strong.
After papermaking, it is preferable to add a water emulsion adhesive such as polyvinyl acetate emulsion, polybutadiene emulsion, etc. for reinforcement. Alternatively, there is also a method in which some of the fibers with a diameter of 5 μm or more are made into heat-fusible fibers, such as ethylene-vinyl acetate copolymer or heat-fusible polyamide fibers, and heat is applied to a temperature sufficient for heat-fusion after paper making. You can take it. In the production of a paper-like sheet material used as an air filter filtration material, the larger the amount of fibers with a fiber diameter of 1 μm or less, the higher the capture rate, but the higher the cost and the lower the paper strength. Therefore, it is preferably 2 to 50% by weight of the total fiber content.

Furthermore, when using fibers made from synthetic polymers, it is necessary to use fibers that do not contain inorganic pigments in order to reduce the volume during incineration. The preferred degree of volume reduction is that the ash content when incinerated at 800°C in the atmosphere is 4.0% by weight.
The weight after incineration must be less than 4% of the weight of the raw material.
% or less.

〔Effect of the invention〕

The air filter of the present invention has a high ability to capture fine particles, does not have high ventilation resistance, and has good bending workability and shape retention properties, so it can be assembled into an air filter in the form of pleats, corrugates, etc. suitable for Furthermore, since the ash content is small, it is easy to incinerate after use.

〔Example〕

The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 Kevlar fiber (Du pant product pulp grade,
3-4 denier, fiber length approximately 2n++++) Disperse 10g in water 11 and use a homogenizer (
Gaulin 15M-87A) was charged at approximately 25°C and circulated 30 times under a pressure of 420 kg/cm2 to obtain a suspension of Kevlar microfibrillated fibers stably suspended in water. mold concentration 1%).

The diameter of microfibrillated fibers in the suspension is approximately 0.4 μm
Met. 0.5 denier (fiber diameter approximately 7 μm), 5.1
70 overlapping parts of cm-long polyester fibers, 3000 parts by weight of the above microfibrillated Kevlar suspension, and 200 parts by weight of water.
0 parts by weight were mixed and stirred to form a slurry, and the slurry was made into paper using a standard square hand paper machine (brass wire 80 mm).
A paper-like sheet material having a basis weight of 75 g/m2 was obtained. The pressure loss and collection efficiency of the obtained sheet material were measured by the following methods. In addition, the incineration residue (
Ash content) was measured.

Pressure loss: The ventilation resistance when air was passed through the filter medium at a flow rate of 4.75 Cm/sec was determined using a water column manometer.

Dust collection efficiency: Dioctyl phthalate particles with an average particle size of 0.3 μm are generated, the air containing these particles is passed through a filter medium at a flow rate of 5.3 Cm/sec, the air is sampled before and after the filter medium, and each Particle concentration was measured and calculated using a multi-dust counter.

Example 2 Microfibrillated Kevlar suspension 15 obtained in Example 1
00 parts by weight, 85 parts by weight of polyester fiber, and 3500 parts by weight of water.
After adding parts by weight, making paper in the same manner, and once drying, 4.
28 parts by weight of an acrylonitrile/butadiene aqueous emulsion having a solid content concentration of 0% was added and suctioned from below the mesh until 1/2 of the emulsion was adhered, and dried to obtain a sheet material.

Comparative Example 1 30 parts by weight of glass micro wool with a diameter of approximately 0.6 μm and a length of 0.4 mm, 0.5 denier (fiber diameter approximately 7 μm),
70 parts by weight of polyester fiber with a length of 5.1 cm and 40 parts by weight of water
After paper making, 700 parts by weight of a 1% aqueous solution of melamine-formalin resin was added to the slurry, and only the amount to be adhered by free fall was adhered to obtain a dry sheet material.

Comparative Example 2 In place of the glass microwool in Comparative Example 1, polyester fiber microfiber (diameter: approximately 1.0 μm, length: 0.0 μm) was used.
A sheet material was obtained in the same manner except that 5 mm) was used.

Measured physical properties of the sheet material are summarized in Table 1.

Table 1 ■

Claims (1)

[Scope of Claims] 1. 2 to 50% by weight of organic fibers with a fiber diameter of 1 μm or less;
An air filter filtration material formed by sheeting a fiber mixture consisting of 50 to 98% by weight of organic fibers with a fiber diameter of 5 μm or more. 2. The air filter filtration material according to claim 1, wherein the organic fibers having a fiber diameter of 1 μm or less are microfibrillated products of rigid linear synthetic polymers or whiskers of rigid linear synthetic polymers. 3. The air filter filtration material according to claim 1 or 2, which has an ash content of 4.0% by weight or less when incinerated at 800°C in the atmosphere.