JP2640898B2 - Synthetic resin porous body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin-based porous body, and more particularly, to a synthetic resin-based porous body having a high porosity, excellent filtration accuracy, and suitable as a filter material.

[0002]

2. Description of the Related Art Since a synthetic resin having a porous structure is lightweight and excellent in workability, it includes structural materials such as building materials, fillers, flotation materials, and wall materials, as well as heat insulating materials, heat insulating materials, and sound insulating materials. Those which are widely used for applications such as, for example, and which have air permeability and liquid permeability are widely applied as various filter media.

[0003] The synthetic resin-based porous material as described above is generally manufactured by a method called a foaming method or a sintering method. By the way, in order to obtain a high-precision filter medium, the pore size must be extremely small. However, it is difficult to obtain a high-precision filtration material having a large pore size produced by a foaming method. Therefore, a synthetic resin-based porous body for high-precision filtration is usually manufactured by a sintering method. This method fills a predetermined mold with a spherical powder of a synthetic resin,
After pressing at a predetermined pressure, the temperature is raised to around the melting point of the synthetic resin, and the spherical powders of the synthetic resin are fused and fixed.

[0004] As a porous body for a filter medium, a porous body having a high porosity is preferable because it has a small pressure loss, can increase a filtration capacity, and is excellent in lightness. However, the porous shape of the synthetic resin-based porous body obtained by the above-described sintering method is determined by the filling state of the spherical powder of the synthetic resin used, and has a relatively regular shape and a low porosity. Never exceed 40%.

In order to obtain a synthetic resin-based porous body having a high porosity by the sintering method, a method of reducing the pressing pressure or a method of reducing the sintering temperature history to reduce the volume of sintering in the aforementioned manufacturing method. Although a method of reducing shrinkage as much as possible is conceivable, the improvement of the porosity obtained by such a method is at most about several percent, the porosity does not exceed 40%, and the porous body is mechanically The strength is remarkably reduced, which is not preferable.

In order to complicate the shape of the pores, if a synthetic resin having a spherical shape is made irregular and filled with a material having a wide distribution, the filtration accuracy is improved, but the packing density is increased. The porosity decreases, which is not preferable.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a synthetic resin porous body which has excellent mechanical strength and high porosity and is suitable as a high-performance filter medium.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a powdery synthetic resin comprising a thermoplastic resin which is substantially spherical and a fibrous substance having a melting point equal to or higher than the melting point of the powdery synthetic resin. This is achieved by a synthetic resin-based porous material characterized in that the powdery synthetic resin forms a basic skeleton structure, has continuous pores, and has a porosity of 40% or more.

The material of the synthetic resin fine particles used in the present invention is desirably a thermoplastic resin having a melting point. Examples of such a material include those of the system such as polyolefin, polyamide, polyester, polystyrene, and polyacryl.

[0010] The fibrous substance used in the present invention is a fine needle-like substance or a short fibrous substance. Examples of the fine needle-like substance include whiskers such as silicon carbide whiskers and potassium titanate fibers. Examples of short fibrous substances include natural fibers such as cotton, hemp, and wool.
Examples thereof include cut fibers of synthetic fibers such as polyolefin, polyamide, polyester, polystyrene, polyacryl, and vinylon; fibrous organic substances such as cellulose acetate; and inorganic fibers such as glass fibers and metal fibers.

In the present invention, the fiber diameter, fiber length and the like of the fibrous substance are not particularly limited. However, it is not preferable that the size or the size of the fibrous substance is too far from the size of the powdery synthetic resin forming the sphere.

The synthetic resin porous body of the present invention is a sparse bulky tissue having continuous pores obtained by homogeneously mixing the powdery synthetic resin and the fibrous substance. The pore structure has a complex skeleton structure composed of powdery synthetic resins, fibrous substances, and voids formed by bonding the powdery synthetic resin and the fibrous substance.

The porosity of the synthetic resin porous body of the present invention is:
It is 40% or more, preferably 50% or more. If the porosity is lower than 40%, the resistance to the passage of the air, that is, the so-called pressure loss is increased, and the clogging is too fast, so that the filter is not suitable as a filter medium. On the other hand, the porosity is 50%
In the above, since the pressure loss is significantly reduced, the filtration efficiency is high.

The synthetic resin porous body of the present invention can be produced, for example, as follows. That is, the spherical powdery synthetic resin and the fibrous substance are uniformly mixed in a mold, and sintering is performed at a temperature slightly higher than the melting point of the powdery synthetic resin. When sintering, the material may be compressed in a mold in advance and temporarily solidified. As for the spherical powdery synthetic resin used here, the one having a small sphere diameter distribution is easy to obtain one having a high porosity and easy to mix uniformly.

In the above method, the porosity and the pore diameter are defined as the sphere diameter of the powdery synthetic resin used, the fiber diameter and the fiber length of the fibrous substance, the mixing ratio of the powdery synthetic resin and the fibrous substance, and the compression ratio. Can be adjusted by appropriately setting. If the compression ratio is too large, the porosity becomes small, which is not preferable.

When the fibrous substance used in the above method has a melting point, the melting point is preferably higher than the melting point of the powdery synthetic resin. When the melting point of the fibrous substance is lower, the fibrous substance is greatly deformed during sintering, and it is difficult to obtain a stable shape having a high porosity.

In the above-mentioned method, a small amount of a binder may be used for compression and solidification before sintering. In this case, after sintering, the binder may be removed by washing or the like. The same applies to the case where, for example, a surfactant, a dispersant, or the like is used for the purpose of uniform dispersion. However, it is not preferable that these additives decompose or degrade at the sintering temperature, and it is preferable to use those having heat resistance.

In order to use the synthetic resin porous body of the present invention as a filter medium or the like, it may be formed by cutting, cutting, slicing or the like as necessary. Therefore, a resin excellent in processability is desirable, and in order to obtain such a resin, it is preferable to use a resin made of a thermoplastic resin such as a polyolefin, a polyamide, or a polyester as the powdery synthetic resin.

[0019]

The porosity of a conventional sintered body composed of only a spherical resin is relatively monotonous and has an upper limit on the porosity, whereas the present invention has an elongated fibrous substance interposed in the spherical resin. In addition, the pore shape becomes irregular, and the porosity increases because there are portions where the spherical resins do not adhere to each other.

The synthetic resin porous body of the present invention, when used for a filter medium, has a small pressure loss due to a high porosity, and has a complicated pore structure, for example, the tip itself of a fibrous substance becomes an obstacle. Therefore, the ability to capture contaminants becomes extremely high.

[0021]

【Example】

Example 1 Powdered polypropylene 10 having an average particle size of 80 to 130 μm
0 parts by weight, 0.5-2 μm in diameter, 10-20 μm in length
Was uniformly mixed with 10 parts by weight of silicon carbide whiskers, and the mixture was charged into a square mold made of brass, and 2 kg / cm
Pressurize with ²
The temperature was raised to 70 ° C. When the temperature reached 170 ° C., the heating was stopped, and the mixture was allowed to cool to room temperature, and then taken out of the mold to obtain a synthetic resin porous body.

The obtained synthetic resin porous body had an average pore diameter of 80 μm and a porosity of 52%. This is 2mm thick
, And punched out in a disk shape to form a strainer element for compressed air.

The obtained strainer element has excellent mechanical strength, is free from breakage or falling off during use, has a small pressure loss of compressed air, and is extremely excellent in capturing foreign substances in the air. The trapping rate of dust and mist on the order of microns was 90% or more.

Comparative Example 1 A synthetic resin porous body was obtained in the same manner as in Example 1, except that the silicon carbide whiskers used as the fibrous substance were not used. The obtained synthetic resin porous body had an average pore diameter of 60 μm and a porosity of 35%. This was formed into a sheet having a thickness of 2 mm in the same manner as in Example 1, and then punched into a disk to form a strainer element for compressed air.

The obtained strainer element could not be put to practical use because the pressure loss of the compressed air was too high. Also, the mechanical strength was weak, and it was broken by applying several pressure impacts.

[0026]

The synthetic resin porous body of the present invention is composed of a spherical powdery synthetic resin and a fibrous substance, has an unprecedentedly high porosity and has a large pore diameter distribution. Therefore, when used as a filter medium, the pressure loss is small, and the filtration efficiency is excellent for the porosity. Further, since fine contaminants can be trapped not on the surface but on the inside, they can be used very suitably as a depth-type filter medium rather than an absolute-type filter medium.

The synthetic resin-based porous body of the present invention is very easy to perform secondary molding such as cutting, cutting, slicing, and the like, so that it can easily cope with any shape.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08L 101: 00

Claims (1)

(57) [Claims] 1. A powdery synthetic resin comprising a thermoplastic resin having a substantially spherical shape and a powdery synthetic resin having a melting point equal to or lower than the melting point of said powdery synthetic resin.
Or a fibrous substance having a high melting point, and the powdery synthetic resin constitutes a basic skeleton structure.
Both have continuous pores, and have a porosity of 40% or more.