JPS5910320A - Filter medium - Google Patents

Abstract

PURPOSE:To provide an air filtering medium having a long service life and high strength and capable of thermal disposal, by forming a triple-layered construction, each of which is a differently constituted layer of a web consisting essentially of ultrafine and combustible synthetic fibers. CONSTITUTION:A web consisting essentially of ultrafine and combustible synthetic staple fibers having 0.1-1.5mu diameters each, is formed by a melt blowing method. These >=1 sheets of webs are laminated into one body to be used. A fiber packing rate of the fiber-layered body is 3-20%, and a ratio of the actually detected surface area SB per unit area to a logical surface area SA is 1>SB/ SA>=0.7, and the number of stape fibers to be laminated in the direction of the thickness of a filter medium is 40-1,000. The fibers of the surface layer are three-dimensionally intersected with each other, and the surface is covered with fine nap-shaped fibers. The fibers in the intermediate layer are two-dimensionally intersected with each other approximately parallelly to the surface layer. The fibers in the lower layer are three-dimensionally intersected with each other more densely than the surface layer. The ratios of the thicknesses among respective layers are preferably 1:1-1/4:(1-1/4).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-performance p-material for air filters, which is made of a laminate of combustible ultrafine fibers and has excellent p-permeability characteristics.

Conventionally, in areas where radioactive materials are handled, such as nuclear power plants and nuclear research institutes, indoor air containing radioactive dust has been
High-performance air filters are used to over-purify and release the air outside, and high-performance air filters are used to over-purify outside air and bring it into clean rooms in hospitals, precision equipment assembly factories, semiconductor industries, etc. ，
It is necessary to collect ultrafine dust of O3 microns or less with high efficiency.

The tear material for high-performance air filters currently in use is a laminate made of fine glass fibers, and there has been no P# for high-performance air filters made of fibers other than glass fibers.

However, it is difficult to improve the amount of dust that can be collected with this glass fiber paper tie material.Furthermore, its strength is low, making it easy to break during handling and use, and since it is non-flammable, it is discarded by incineration. Disposal of used filters has become a problem. In particular, used filters that contain radioactive dust cannot be disposed of, so they are currently being stored, and securing storage space is also becoming an issue.

Therefore, there has been a strong desire to develop a flammable, high-performance tear material for air filters that does not break during handling or use, has a large dust collection capacity, has a long life, and can be incinerated.

Tokorochi's current high-performance air filters must be able to collect more than 99.97% of ultrafine particles of 0.3 microns in a state with extremely low ventilation resistance of 501111IH20 or less, so up until now, ultrafine glass fibers have been used. This could only be achieved with the papermaking type.

The present inventors have conducted intensive research to develop a high-performance air filter lacrimal material that has such performance and characteristics using combustible fibers, and have found that within a specific fiber diameter range of combustible synthetic fibers, and We have succeeded in developing a tear material for high-performance air filters that satisfies the performance requirements of current high-performance air filters only in a specific structure, has a long life, is highly strong, and can be incinerated.

The present invention relates to a P material consisting of a fiber laminate made by overlapping and integrating a single web or a plurality of webs mainly composed of ultrafine combustible synthetic fibers with a single fiber diameter of 01 to 15 microns, the fiber filling of the P material being ratio is 3 to 20%, measured surface area SB and theoretical surface area SAO of constituent fibers per unit area of P material
The ratio is 1〉d and 07, the number of laminated single fibers in the thickness direction of the p material is 40 to 1000, and the surface layer of the p material has the minimum three-dimensional structure that allows all the constituent fibers to form a single body. The upper layer 1 is an intertwined rough layer with fine fluff formed on its surface, the middle layer 2 is a middle layer 2 in which the constituent fibers are mainly intertwined in two dimensions, and the upper layer is in which the constituent fibers are mainly intertwined in three dimensions. This p-material is characterized by having a three-layer structure with the lower layer 3 forming a dense layer.

In the present invention, the web refers to a nonwoven fabric made by papermaking of staple fibers, a long fiber nonwoven fabric made by laminating melt-spun fibers, a web formed by carding needle punching, etc., and a web formed by one method of melt blowing is particularly preferable. This makes it easy to obtain ultrafine long fibers that meet the purpose of the present invention.

This is because it is easy to obtain a web that has uniform basis weight, thickness, etc., and is less prone to cracks and pinholes. Further, it is a web made of ultrafine fibers obtained by dissolving and removing one of sea-island fibers made of two components such as a polyamide-based component and a polyester-based component, or a web made of ultrafine fibers obtained by a peel-type composite spinning method. Good too.

The fibers constituting such a web have a single fiber diameter of 01 to 1
It is necessary that the fiber be comprised mainly of ultra-fine combustible synthetic fibers having a diameter of 5 microns, preferably in the range of 02 to 10 microns. Here, the combustible synthetic fibers in the present invention include:
Highly combustible and flame-retardant synthetic fibers are used, not only those that are particularly easy to combust (they may also be those that can be combusted by applying high temperature. Conversely, when using easily combustible fibers, It is preferable that the material be treated with a flame retardant.

This is effective as a fire prevention measure during use, and this processing does not impede the performance of the p-material of the present invention. In particular, thermoplastic synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and polyacrylic fibers are preferable as the main combustible synthetic fibers, and among these, polyester synthetic fibers are the most preferable in terms of dimensional stability. .

The single fiber diameter of the combustible synthetic fiber that should be the main body is 01
If it is less than a micron, the adhesion between the fibers is strong, so
This is not preferable because the density of the P material and the fiber laminate to be formed becomes too high, and although the required collection of ultrafine particles is ensured, the initial ventilation resistance increases.

On the other hand, if the single fiber diameter exceeds 15 microns, the density of the fiber laminate made of the fibers becomes too small, making it difficult to collect ultrafine particles with high efficiency. In the present invention,
A particularly preferred monofilament diameter of the combustible synthetic fiber to be the main component is in the range of 0.2 to 1.0 microns.

One or two webs 4i mainly composed of ultrafine combustible synthetic fibers having a single fiber diameter of 01 to 15 microns are laminated and integrated to form a fiber laminate.

In the fiber laminate mainly composed of the above-mentioned combustible synthetic fibers,
All of the constituent fibers may be the same type of combustible synthetic fiber with a single fiber diameter of 01 to 1.5 microns, but different types of fibers may be mixed. It is preferable that 30% or less, preferably 20% or less, of fibers of the same type or different types having a single fiber diameter of 2 to 10 times are mixed. These thick fibers play a reinforcing role for the plastic material, and are also useful in preventing extremely thin single fibers from adhering to each other and preventing a sudden increase in ventilation resistance.

What is important in the present invention is that the darning fiber laminate satisfies the following requirements.

density, ρ' is the apparent density of the fiber laminate. ) is in the range of 3 to 20%. If the fiber filling rate is less than 3%, extremely fine dust cannot be collected reliably, and the tear material for a high-performance air filter of the present invention cannot be obtained. Furthermore, if the fiber filling rate exceeds 20%, the initial ventilation resistance will increase, causing clogging in a short period of time, shortening the life of the p-material, and making it unsuitable for practical use. The most preferred fiber filling rate is 5 to 15%.

Second, the actual surface area S of the constituent fibers per unit area of the p-material
The ratio of B to the theoretical surface area SA is in the range of 1>, 5≧0.7. Here, the actual measured surface area is the value measured using a specific surface area measuring device that calculates from the adsorption amount of NQ gas, and the theoretical surface area is the value calculated from the weight of the unit area, the diameter of the constituent fibers, and the denier. is the total surface area. This surface area ratio represents the degree of convergence and adhesion of the fibers constituting the fiber laminate, and this value is preferably 07 or more (or should be 08 or more. If the surface area ratio is less than 07, the fiber laminate It is undesirable because the fibers that make up the fibers adhere to each other to form a large number of thicker fibers, which significantly reduces the efficiency of fine dust aggregation. Because of their strong cohesive force, there is a strong possibility that they will become bundled fibers that adhere to each other.Therefore, in the present invention, by dispersing the tightly bundled fibers of ↑ ultrafine fibers into a monofilament state or a state close to it, The surface area ratio is set to 07 or more.For example, it can be obtained by spraying high-pressure water on a microfiber web produced by one-way melt blowing.

Thirdly, the number of laminated single fibers in the thickness direction of the P material is 40 to 1000.
This is within the scope of the book. When the number is less than 40, the density of the p-material becomes too small, making it difficult to collect fine dust with high efficiency.

Moreover, if the number is 1000 or more, the density of the P material becomes too large and the initial ventilation resistance increases, which is not preferable. Note that the term here refers to the number of laminated fibers.

Furthermore, the surface of the p-material of the present invention has minimal three-dimensional entanglement that allows all the constituent fibers to form an integral body. That is,
The constituent fibers on the surface of the p-material are three-dimensionally entangled, with fibers parallel to the surface of the p-material and fibers perpendicular to the surface of the p-material intertwined with each other, forming the entire surface layer. The extent of this does not extend to the inner layer of the p-material. In addition, its surface is covered with fine fluff-like fibers made of constituent fibers.

Therefore, the surface layer has a coarse density. The fluffy fibers may be cut or looped, and most of the fluffs have a length of several lengths or less, preferably one length or less. The surface layer covered with the fuzzy fibers and the three-dimensionally intertwined layer form the upper layer 1.

This soil layer preferably has a thickness of about 1 to 1 the thickness of the entire door material.

2 The middle layer 2 below the upper layer (the constituent fibers are intertwined mainly two-dimensionally. In other words, the fibers forming the middle layer are intertwined almost parallel to the surface of the material. This middle layer 11 has a thickness of m ~100 is preferable.However, the boundary between the upper layer and the middle layer does not have to be clear, and it is normal for the upper layer to gradually change to the middle layer.

Next to the middle layer, there is a lower layer 3 in which the constituent fibers are mainly intertwined three-dimensionally to form a denser layer than the upper layer. In other words, the lower layer has no surface VC microfuzz like the upper layer. Structure 1 1 in which the constituent fibers are in close contact with each other.

It becomes. The thickness of the lower layer is preferably m to i of the thickness of E material, but the boundary between the middle layer and the lower layer does not have to be clear.

As described below, the p-material of the present invention has a three-layer structure of an upper layer, a middle layer, and a lower layer, and the thickness ratio of each layer is preferably lfl~blue:1~1.

In order to obtain such a spruce material of the present invention, for example, single fibers with a diameter of 0.1 to 1.0 mm are produced by a single melt-blowing method.

A web consisting mainly of ultra-fine combustible synthetic fibers of 15 microns, either alone or laminated in a neem zone, is in a circular or reciprocating motion parallel to the fiber laminate on both sides. High pressure water with a gauge pressure of 2 to 50 KSt/Ivy 2 is sprayed from a nozzle group with a diameter of 01 to 0.5711111. This water pressure is appropriately selected depending on the basis weight and other conditions of the laminate. This spraying treatment is performed at least once on each of the front and back sides of the fiber laminate, but preferably the number of times the spraying treatment is performed on the front side is greater than on the back side. It is also preferable to gradually reduce the injection pressure from the initial pressure.
In order to obtain a one-material structure according to the present invention, at least 210I
Ib2 or higher is required. It is also preferable to interpose a mesh between the fiber laminate and the nozzle group to finely disperse the high-pressure water.

In the P material of the present invention, as mentioned above, soil layer, middle layer,
The lower layer has a three-layer structure, the upper layer is a rough layer whose surface is covered with micro fluff and the constituent fibers are intertwined three-dimensionally, the middle layer is a layer in which the constituent fibers are two-dimensionally entangled, and the lower layer is the constituent fibers. are three-dimensionally intertwined to form a denser layer than the upper layer, so when gas containing dust flows from the upper layer of the F material to the lower layer, it gradually becomes denser after passing through the coarser parts of the P material. Because the gas flows to the inner layer of the P material, there is no chance of dust particles getting caught only on the surface and causing clogging 9, unlike with conventional P materials that mainly use surface filtration. With this ability, the amount of p1 dust collected is greatly increased, and the life of the filter is significantly improved.

In addition, the door material of the present invention has a single fiber diameter, fiber filling rate, SB/
SA, when the number of laminated single fibers in the thickness direction is within a specific value range and the f material is viewed as a whole, the ultrafine fibers are at an appropriate density and each single fiber is dispersed without bunching. , there are no extremely large or extremely small holes.

Therefore, an advantage A can be obtained in that the efficiency of collecting fine dust is high despite the initial ventilation resistance being low.

Furthermore, while conventional materials cannot be disposed of by incineration, the f-material of the present invention is made of combustible synthetic fibers and forms a web, so it is possible to dispose of used door materials by incineration. There is almost no leftover pickle left.

Furthermore, since the door material of the present invention is made of synthetic fiber,
It is not brittle or easily broken like glass fiber, and is extremely strong, so it will not break during handling or use.

Next, the performance of the f-material of the present invention will be shown by examples.

Example Five polyester fiber webs (fabric weight: 30z/m2) produced by the melt-blowing method and mainly having single fiber diameters of 0.1 micron, 0.8 micron, and 1.5 micron were laminated and heated at a constant width at 160°C. I applied pin tenter treatment. While moving this on a 50 mesh wire mesh moving at a speed of 1771/H'sH, high pressure water with a gauge pressure of 2 to 30Ky10IIL2 is applied from a nozzle group located 40 meters above it in the vacuum zone. was treated by injection. The nozzle group consists of 5 nozzles in the horizontal direction and 6 rows in a staggered manner at 2 mra intervals in the vertical direction, each having a nozzle diameter of 0.15 ml, with 8 nozzles in diameter moving in a circular motion at a rate of 250 times/minute. The injection treatment of high-pressure water to the laminate was performed a total of 5 times on the front and back sides alternately. Incidentally, the process 1111 to the back side was carried out through an 80-mesh wire mesh. It was then dried at 100°C. The results of measuring the collection efficiency and ventilation resistance of the stearic acid particles having a particle size of 0.3 m3 and 1 F of the obtained material 1 are shown in the following table.

17-123 Procedural amendment (formality) November 19, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office■, Small case indication patent application No. 118636/1982 2, Name of the invention Uto material 3, Person making the amendment Relationship to the case/Patent applicant: 1-2-6 Dojimahama, Kita-ku, Osaka-shi, Osaka (003) Asahi Kasei Industries, Ltd. President Teru Miya 4; Agent: 1-4 Yujo-cho, Chiyoda-ku, Tokyo No. 1 Sanshin Building Room 204 Telephone 501-2138 Toyota Naigai@
Yoshio Office (5114+) Patent Attorney Yutaka 1) Yoshio 5, Date of amendment order A. 1, 1937, October 7, 6, Item 7 of the brief explanation of the drawings of the specification subject to the amendment, Contents of the amendment After the song number on the first line of page 18 of the specification, insert a brief explanation of the drawings shown below.

[4. Brief explanation of the drawings FIG. 1 is a sectional view showing an example of a furnace material according to the present invention.

14441 upper layer, 2 front middle layer, 311 ma! lower layer,”−
1′;

Claims (2)

[Claims] (1) In material F, which is made of a fiber laminate made by overlapping and integrating a single web or a plurality of webs mainly composed of ultrafine combustible synthetic fibers with a single fiber diameter of 01 to 15 microns, the fibers of material P Filling rate is 3 to 20% Measured surface area B of constituent fibers per unit area of p material Ratio of sB to theoretical surface area sAO is 1>, ≧0.7, p
The number of laminated single fibers in the thickness direction of the material is 40 to 1,000, and the surface layer of the P material is three-dimensionally entangled to the minimum extent that allows all the constituent fibers to form a single body. The upper layer 1 is a coarse layer in which fine fluff is formed, the middle layer 2 has constituent fibers intertwined mainly two-dimensionally, and the constituent fibers mainly intertwine three-dimensionally to form a denser layer than the upper layer. A p-material characterized by having a three-layer structure including a lower layer 3. (2) The p-material according to claim 1, wherein the web mainly composed of ultrafine combustible synthetic fibers having a single fiber diameter of 01 to 15 microns is a polyester long fiber web obtained by a melt blowing method.