JPS58109540A - Preparation of porous body - Google Patents

Abstract

PURPOSE:To easily obtain a porous body having a sharp pore size distribution, by a method wherein a thermoplastic resin powder is dispersed in a high b.p. dispersing medium to form a paste and, after this paste is cast and sintered at a temp. lower than the b.p. of the dispersing medium, the dispersing medium is removed. CONSTITUTION:100pts.wt. thermoplastic resin powder such as polyvinyl chloride powder or polyethylene powder is dispersed in 50-500pts.wt. high b.p. dispersing medium (e.g. silicone oil or machine oil) having a b.p. higher than a temp. 20 deg.C lower than the m.p. of said resin. The obtained pasty substance is cast on an iron plate and introduced into a heater to carry out sintering treatment at about 150-400 deg.C. In the next step, the dispersing medium is removed by vacuum heating to obtain an objective porous body. In this case, by increasing the amount of the dispersing medium, the pore size of the porous body can be increased and, by reducing the amount thereof, the pore size thereof can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION More particularly, the present invention relates to a method for producing a porous body using a sintering method in which the pore diameter can be controlled extremely easily and the pore diameter distribution is extremely sharp.

Conventionally, the so-called sintering method, in which thermoplastic resin powder is thermally fused under appropriate heating conditions to form a porous body, has a particle size of several 10
This has been applied to the case of thermoplastic resin particles with a diameter of μ or more, but when the particle size of the thermoplastic resin is several μ or less, the agglomeration of thermoplastic weight-resistant particles is so severe that it is impossible to obtain a porous body. This is possible, and since the particle size of the thermoplastic resin particles and the pore size of the porous body are approximately the same in the sintering method,
Conventionally, it was thought that a porous body with a small pore diameter of several microns or less could not be obtained by the sintering method.

In view of the current situation, the present inventor has arrived at the present invention as a result of intensive studies aimed at providing a simple manufacturing method for a porous body that can easily produce a porous body with a small pore diameter of several microns or less using a sintering method. The gist of the mekoro is that thermoplastic resin powder is dispersed in a high boiling point dispersion medium having a boiling point higher than at least 20°C lower than the melting point of the resin to form a paste. The method of manufacturing a porous body is characterized in that the porous body is cast and sintered at a temperature lower than the boiling point of the dispersion medium, and then the dispersion medium is removed.

Examples of the thermoplastic resin powder used in the present invention include polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate, ABS resin, polycarbonate, and polyvinylidene fluoride (abbreviated as PVDF).

In addition, the dispersion medium for dispersing the thermoplastic resin powder to form a paste must be a poor solvent for the thermoplastic resin to be used, and a boiling point at least higher than the melting point of the resin to be used! O'G is selected from high boiling point solvents at higher temperatures than lower temperatures. The temperature at which the paste-like material is sintered is preferably at least 20°C lower than the melting point of the resin used, and at most 2'OO'C higher than the straining point of the resin used. Due to shortcomings. In other words, the high boiling point dispersion medium for thermoplastic resin powder in the present invention is not limited to the specific examples below, but is essentially a poor solvent for the resin powder used, and a temperature at which the paste-like product and sintering process are performed. A material having a boiling point higher than that may be appropriately selected. Specific examples include dimethyl silicone (silicone oil), machine oil, tetralin, wax (high-grade paraffin), glycerin, etc. For example, dimethyl silicone (silicone oil) is used as a solvent for polyvinyl chloride powder. ), machine oil, and wax (high-grade paraffin) can be used.
Dimethyl silicone and machine oil are preferably used as dispersion media for polyolefin powders such as polyethylene and polypropylene, and tetralin and machine oil are suitably used as dispersion media for polyethylene terephthalate powder.

To carry out the method for producing a porous body of the present invention, first, 50 to 50% of the above dispersion medium is added to 100 parts by weight of the thermoplastic resin powder.
00 parts by weight, preferably 100 to 300 parts by weight, are added using a mixer or the like and thoroughly mixed to form a paste. In this case, by appropriately changing the amount of dispersion medium added, 0.1
It is also possible to fully adjust the pore size in the range of ~10μ. This is because the pore size can be increased by increasing the amount of dispersion medium, and conversely, the pore size can be adjusted to be smaller by decreasing the amount of dispersion medium.

Next, the paste prepared as described above is cast onto an iron plate or coater to a thickness of about 10 to 1000 μm, preferably about 100 to 500 μm, and introduced into a heater such as a sintering furnace. Then, the sintering treatment is carried out under an atmosphere and conditions of 160 to 400° C., preferably 200 to 230° C., for several seconds to several tens of minutes. The sintering temperature in this case is
The temperature is preferably in the range from above the straining point of the resin used to 200° C. higher than the melting point, and must be lower than the boiling point of the high-boiling dispersion medium used.

It should be noted that sintering at a temperature higher than the upper limit temperature of the above-mentioned preferred range is undesirable because the wood and fibers decompose or fuse.

The sintered product thus obtained forms a type of solid solution and contains a high boiling point dispersion medium, so it can be heated to a temperature of 0 to 500 tmnHP while it is on the iron plate or coater or after it is removed from the iron plate or coater. The high boiling point dispersion medium may be volatilized under reduced pressure or extracted and removed using a relatively low boiling point solvent, and then dried.

As a relatively low boiling point solvent for extracting and removing the high boiling point dispersion medium remaining in the sintered product, use a solvent that has good compatibility with the high boiling point dispersion medium and does not swell or dissolve the resin used. Organic solvents are used that do not cause oxidation. Specifically, CFCs, methanol, ethanol, acetone, etc. can be used for dispersion media such as machine oil and silicone oil, and lower hydrocarbons such as gasoline, ethanol, and ether can be used for dispersion media such as tetralin. , ethyl acetate, aromatic solvents such as xylene, toluene, benzene, etc. can be used. Furthermore, for dispersion media such as glycerin, alcohols, ethyl acetate, and ethers can be used, and for dispersion media such as wax (higher paraffin), alcohols, lower halaffins such as hexane, aromatic substances such as xylene, and toluene can be used. Group solvents can be used.

As described in detail above, the production method of the present invention not only allows for the easy production of porous bodies with small pores having an average pore diameter of several microns or less, but also enables adjustment of the average pore diameter, which was difficult in the past. This negates the industrially valuable and remarkable effects that can be achieved by changing the amount of dispersion medium.

Next, the present invention will be specifically explained using Examples (from Example C).

Example 1 High density polyethylene (melting point 137°C, M = 0.3+
, l'=0.95) (average particle size 1μ) 1
00 parts by weight of dimethyl silicone (boiling point 250°C) as a high boiling point dispersion medium in the respective amounts shown in Table 1 below were added separately and mixed well to form a paste.
After casting to a thickness of 500 μm, heating was performed under the sintering conditions shown in Table 1 below to obtain a sheet-like product. Each of the obtained sheets was immersed in Freon to extract and remove the high boiling point dispersion medium, dimethyl silicon, to obtain porous membranes shown in Table 1 below.

As can be seen from the results in Table 1, the dispersion “b50~50
In the case of 0 parts by weight, a porous sheet with a small pore diameter was obtained by appropriately selecting the sintering conditions, but in the case of 600 parts by weight of the dispersion medium, the pores became slightly larger, which was not desirable.

Example 2 100 pieces of finely pulverized granules (average particle size 1μ) of polyvinyl chloride (gelling temperature 180°C) were added to 100@Ichibu as a high boiling point dispersion medium, including DOA% machine oil, as shown in Table 2 below. The high grade waxes were cooled and mixed well to form a paste, and each of these pastes was cast to a thickness of 200μ, and then sintered at 200°C for 5 minutes to obtain a sheet.

Each of the obtained sheets was immersed in ether to extract and remove the high boiling point dispersion medium, to obtain a porous membrane shown in Table 2 below.

Table 2 Example 3 Polypropylene (melting point 176°C), polyethylene terephthalate (melting point 267°C), ABS (gelling temperature 2
00°C), polycarbonate (melting point 220°C), PV
Machine oil (
100 parts by weight (boiling point: 300°C) were added and mixed thoroughly. After casting each paste to a thickness of 500μ, polypropylene was cast at 200°C for 10 minutes, polyethylene terephthalate was heated at 280°C for 10 minutes, and ABS was cast at 200°C for 10 minutes. 225°C for 10 minutes, polycarbonate at 240°C for 8 minutes, PV
DF was sintered at 225° C. for 10 minutes to obtain a sheet-like product. Each of the obtained sheets was immersed in ether to extract and remove the high boiling point dispersion medium, thereby obtaining porous membranes each having a pore size of 01 to 1 μm.

Patent applicant Mitsubishi Plastics Co., Ltd. Agent: Patent Attorney Tsunebe Ogawa

Claims (1)

[Claims] The thermoplastic resin powder is heated at least 2 times higher than the melting point of the resin.
It is dispersed in a high boiling point dispersion medium having a boiling point higher than a temperature lower than 0°C to form a paste, and this paste is cast and sintered at a temperature lower than the boiling point of the dispersion medium. A method for producing a porous body, characterized by removing a dispersion medium.