JPS6247048B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-performance overmaterial, and more particularly to an organic high-performance overmaterial with excellent overflow properties, high reliability, and easy moldability. Conventionally, various types of filter materials have been used for the purpose of removing dust from the air and creating a clean environment. Among these, areas that require ultra-fine dust removal, such as clean rooms, clean benches, hospital sterile rooms, and radioactive dust removal from nuclear power plants, which require a highly clean environment that removes fine dust, are 1 μm or less. In order to collect dust with high efficiency, a filter material with a small fiber diameter is required, and a non-woven filter material made of an inorganic material such as glass micro wool is used. However, since such overmaterials are composed of rigid glass with poor flexibility, they tend to break during handling or use, resulting in problems such as reduced dust collection performance and re-scattering of collapsed microwool. It is said that On the other hand, such overfill materials are difficult to process for the same reason, and the disposal of the overfill materials after use cannot be incinerated, which is a big problem, especially in the nuclear power field. In addition, in producing overmaterials made of these glass microwools, it requires a large amount of energy to turn the glass into microwools, which is expensive, and since the surface of the microwools is smooth, it is difficult to produce them alone. It is difficult to make paper, and requires a roughened surface and a binder. On the other hand, as an organic filter material, a filter material using oriented polyester microfibers is also provided, for example, as disclosed in US Pat. No. 3,382,305. However, such microfibers do not have a rough surface layer on their surface and do not have fibrils connected in a branched manner, so they have poor paper-making properties, and when applied to a paper machine, they have poor peelability from the wire, and The overfill materials obtained by this process also have low porosity and strength, and for this reason, the actual overfill performance is poor. The present inventors have overcome the above-mentioned drawbacks of conventional overfill materials for fine dust and ultra-fine dust, and have worked diligently to develop a high-performance organic overfill material that is easy to form, has excellent overflow characteristics, and is highly reliable and easy to form. As a result of study, the present invention was arrived at. That is, the present invention provides an overmaterial made of pulp made of fibrous fibrils whose cross section is irregular and has an uneven surface, at least a portion of which is connected in a branched manner, The overfill material is characterized in that the porosity of the overfill material satisfies the following equation (), and the porosity of the overfill material satisfies the following equation (). 0.05μm≦fibril average fiber diameter≦5μm
...() 0.90≦Porosity≦0.98 ...() First, the overfill material of the present invention is composed of fibrous fibrils whose cross section is an irregular uneven surface, and at least some of the fibrils are connected in a branched manner. It is obtained by making paper from the pulp. Here, the fibrous fibril may be any polymer as long as it has fiber-forming properties, but
Preferably it is a linear aromatic polyester. Specifically, such linear aromatic polyesters include:
Polyethylene terephthalate, polyethylene terephthalate/isophthalate, polyethylene terephthalate/hexahydroterephthalate, polyethylene terephthalate/5-(sodium sulfo)isophthalate, poly(P-hexahydroxylylene terephthalate), poly(diphenylol propane isophthalate), and polyethylene naphthalene Dicarboxylates (especially 2 and 6
and 2,7-isomer derivatives and hexamethylenebibenzoet), among which bifunctional aromatic carboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid are used as acid components, Linear aromatic polyesters containing glycol as a glycol component, such as ethylene glycol, trimethylene glycol, tetramethylene glycol, and hexamethylene glycol, are preferred, especially those with the general formula [n represents an integer of 2 to 6] A polyester whose main constituent is a repeating unit represented by the following is used, and a part of its acid component and glycol component are replaced with other bifunctional carboxylic acids and other glycol components, respectively. It goes without saying that you can replace it with . These polyesters may contain additives such as matting agents, thickeners, pigments, etc., if desired. The cross section of the fibril has an irregularly uneven surface along the axial length of the fibril. In other words,
The fibril surface is a shallow rough surface in the form of a stripe along the length of the fibril axis, or a deeply cut or protruding rough surface. In this way, since the cross section of the fibrils has an irregular uneven surface, the fibrils are held together during paper making, resulting in good paper-making properties. Since there is no directional anisotropy, the air ventilation resistance is low, and the surface area of the constituent fibrils is large, it becomes extremely easy to collect dust. Such an effect cannot be achieved with a fibril that does not have an uneven surface with an irregular cross section. Further, at least a portion of the fibrous fibrils of the present invention are connected in a branched manner, which promotes intertwining of the fibrils, improves paper-making properties, and increases strength. Since the high-performance overfill material of the present invention is essentially composed of fibrous fibrils, it can obtain excellent overflow properties, but the average fiber diameter of the fibrils is 0.05 μm or more and 5 μm or less, more preferably 0.1
The thickness is preferably from μm to 3 μm. If the average fiber diameter of the fibrils is less than about 0.5 μm, the stiffness of the fibrils will be small, so the resulting overfill material will not have the desired bulk and the pressure loss will increase, while if it exceeds about 5 μm, it will be difficult to collect fine dust. Performance deteriorates significantly. The variation in the fiber diameter Df of such fibrils σ σ = (Df ₂ )−(Df) ² /(Df) ² ...(
) is 0.7 or less, preferably 0.4 or less. When the fibril fiber diameter variation σ exceeds about 0.7, the relationship between air ventilation resistance and collection performance, that is, the overfill properties as a overfill material deteriorates. Furthermore, the porosity of the overfill material obtained by paper-making a pulp-like structure made of such fibrous fibrils: Porosity = 1 - basis weight of overfill material (g/m ² )/thickness of overfill material (cm) x 10 ⁴ × true specific gravity of pulp (g/cm ³ )...
...() must be 0.90 or more and 0.98 or less, preferably 0.92 or more and 0.97 or less. If the porosity is less than about 0.90, the interaction between the fibrils becomes significant and the transmissibility deteriorates, while if it exceeds about 0.98, the porosity becomes too large and the permeability described below deteriorates (increases), and the resulting porosity deteriorates. The dimensional form of the product cannot be maintained. As described above, the present invention is a filtration material obtained by paper-making a pulp consisting of fibrous fibrils with a substantially small fiber diameter, and it is essential for the filtration material to have a high porosity in order to exhibit the filtration properties. This is a requirement. The filter material of the present invention detailed above has an oriented structure obtained by melt-spinning and stretching a mixture of, for example, a linear aromatic polyester and an organic compound that is incompatible with the polyester and soluble in an alkaline solution. After cutting the fibers to an appropriate fiber length, treating them with an alkaline solution and beating them into pulp, this pulp can be obtained by making paper using a wet paper making method that is widely used, for example, for natural pulp paper (details). (See Japanese Patent Application Nos. 54-72180 and 54-120006). In this case, the fibers are preferably hollow fibers or flat fibers, and in particular, the thickness of the fibers is preferably 6 μm or less in order to carry out the alkali treatment efficiently and quickly. In addition, the fibers can be heat-treated at a specific temperature [softening point temperature (°C) of organic compound +20°C to softening temperature (°C) of linear aromatic polyester -10°C] at any stage before the alkali treatment. It is preferable to bleed out. The filtration material of the present invention has low resistance to fluid passage, excellent impurity collection performance, is flexible and easy to handle, is organic and has good moldability, and can be easily incinerated after use. It's extremely easy. Therefore, this filter material is suitable for use in removing fine dust in the air such as aerosols or impurities in wet liquids. EXAMPLES The present invention will be specifically explained in Examples below, but the present invention is not limited to the Examples below. In addition, in the examples, the properties of the overmaterial were measured by the following method. Fibril average fiber diameter (μm): Photograph any position of the overfill material after papermaking with a scanning electron microscope (magnification: 2000x), randomly extract the diameter of the fibers, read 20 points per sheet, and calculate the arithmetic average of 200 points. I asked for it. Variation σ in fiber diameter: The variation σ in fiber diameter was calculated from the fiber diameter Df read by the above method using the above formula (). In the above formula, Df is the fiber diameter at each point, and Df is the average fiber diameter. Porosity: Calculated using the above formula () from the basis weight of the overfill material (g/m ² ), the thickness of the overfill material (cm), and the true specific gravity of the pulp (g/cm ³ ). Pressure loss △P (mmH ₂ O); Linear velocity of air to overfill material
The ventilation resistance when aerated at 4.75 cm/sec was determined using a water column manometer. Transmittance (Co/Ci): Generate dioctyl phthalate (DOP) particles with an average particle size of 0.3 μm, and
A part of the air was collected before and after the overfilling at 4.75cm/sec, and the number concentration of DOP particles (Co, Ci) was measured using a 4100 multi-gost counter manufactured by Dan Scientific Co., Ltd., using the following formula. Calculated. η = Number concentration on the outlet side (pieces/) / Number concentration on the inlet side (pieces/) Strength of overmaterial (Kg/mm ² ); Tensile strength of overmaterial (Kg/mm 2 ) Using a testing machine, the strength was determined when the sample was stretched and cut at a sample width of 15 mm, a grip interval of 50 mm, and a pulling speed of 50 mm/min. Example 1 Polyethylene terephthalate (intrinsic viscosity 0.65 as measured in O-chlorophenol solution at 35°C) obtained by a conventional method was metered with a gear pump at 295°C and then fed to a kneading screw heated to 285°C. On the other hand, a mixture of sodium alkylsulfonates having 8 to 20 carbon atoms and an average carbon number of 14 was metered at 150°C using a gear pump and then fed to the kneading screw heated to 285°C. The mixing ratio of sodium alkylsulfonate to polyethylene was 4% by weight. The blended polymer mixed with a kneading screw was extrusion molded to obtain a chip-shaped molded product. After drying the obtained chips, using a nozzle having a horseshoe-shaped opening in which a part of the annular slit is open, the discharge amount was varied in two levels, and melt-spun according to a conventional method to form hollow fibers in two levels. Obtained. These raw yarns were doubled, drawn, and heat set to obtain a tow of 170,000 de (single fiber deniers: 1.5 and 3.2 deniers). After cutting this tow into 3 mm pieces with a guillotine cutter, it was poured into a caustic soda aqueous solution (30 g/) maintained at 98°C ± 1°C at a bath ratio of 1:100, treated for a specified time (2 levels) with stirring, washed with water, and dried. After that, the slurry was dispersed in water, and the slurry with a concentration of 1% was beaten using Discliff Aina manufactured by Noya Riki Co., Ltd. Polyfix (polyamide epichlorohydrin binder, Showa Kobunshi) was added to the pulp slurry based on the pulp weight. KK)
(manufactured by Toyo Seiki Co., Ltd.) was added as an internal binder in an amount of 1% by weight, the pulp concentration was adjusted to 1 g/79, and the pulp was formed into paper using a Tatsupi standard sheet machine manufactured by Toyo Seiki Co., Ltd. and dried. For comparison, glass micro wool was also produced in the same manner as described above, except that the wool concentration was 1.84 g/min. The thus obtained overfill was photographed using a scanning electron microscope (magnification: 6000x). As is clear from FIG. 1 (Experiment No. 1), the overfill material according to the present invention has an irregularly uneven surface in its cross section and is composed of fibrous fibrils at least partially connected in a branched manner. The paper-making properties are also good. On the other hand, as is clear from FIG. 2 (Experiment No. 4), the surface of the overmaterial made from glass micro wool was smooth, and it was difficult to separate it from the wire during paper making. The experimental conditions and results are shown in Table 1. As is clear from Table 1, the average fiber diameter is 0.05μ
The relationship between pressure drop and transmittance is better for overmaterials made from pulp made of fibrous fibrils with a size of 5 μm or more and 5 μm or less than for conventional overmaterials made of glass micro wool (experimental results). No.
1-3, see 4-6). On the other hand, the average fiber diameter is
Overmaterial made from pulp made of fibrous fibrils of less than 0.05 has a large pressure loss (Experiment No.
10) If the diameter exceeds 5 μm, the transmittance is very poor (Experiment No. 9). In addition, although good results have been obtained with the overfill material of the present invention with a porosity of 0.9 to 0.98, those with a porosity of less than 0.9 have inferior performance in terms of pressure loss than the conventional overfill material made of glass micro wool ( Experiment No.
8) If it exceeds 0.98, it is difficult to maintain the dimensional form of the overfill material (Experiment No. 12).

【table】

[Table] Example 2 Experiment of Example 1 except that no internal binder was added
Paper-making was carried out in the same manner as No. 2 and No. 5 to obtain overfill material. The results are shown in Table 2. As is clear from Table 2, in the paper made from pulp made of fibrous fibrils (Experiment No. 2'), wire peeling was good due to the mutual binding and entanglement of the fibrils, and the strength of the overmaterial after drying was also good. It is high and has good ground. On the other hand, in the paper made from glass micro wool (Experiment No. 5'), the surface of the micro wool is smooth and no branching is observed, so the fibers do not get caught or entangled with each other, and the wire peeling is poor and dry. The strength of the later overfill material is weak and the formation is somewhat poor.

【table】 [Brief explanation of the drawing]

Figure 1 is a scanning electron micrograph (6000x) of the surface of the overfill material made from polyester pulp according to an embodiment of the present invention, and Figure 2 is a photograph of the overfill material made from glass micro wool. This is a scanning electron micrograph of the surface (2000x magnification).

Claims (1)

[Scope of Claims] 1. An overmaterial made of pulp made of fibrous fibrils having an irregular uneven surface in the cross section, at least a part of which is connected in a branched manner, An overmaterial characterized in that the average fiber diameter of the overmaterial satisfies the following formula (), and the porosity of the overmaterial satisfies the following formula (). 0.05μm≦fibril average fiber diameter≦5μm
...() 0.90≦porosity≦0.98 ...() 2. The filter material according to claim 1, wherein the fibrous fibrils are composed of linear aromatic polyester. 3 The linear aromatic polyester has the following general formula [n represents an integer of 2 to 6] The overmaterial according to claim 2, which is a polyester mainly containing repeating units represented by the following. 4. The overmaterial according to claim 1, wherein the fiber diameter variation σ of the fibrils is 0.7 or less.