JPH093236A - Ultra high molecular weight polyethylene porous body - Google Patents

Abstract

(57) [Summary] [Structure] A large number of cauliflower-like ultra high molecular weight polyethylene resins having an average particle size of 250 µm to 400 µm and a viscosity average molecular weight of 500 × 10 ^{4 to} 650 × 10 ⁴ are sintered and formed. A porous body made of ultra-high molecular weight polyethylene, characterized in that continuous pores are formed. [Effect] A homogeneous porous material having a low bulk specific gravity is obtained, pressure loss is kept low, and mechanical strength such as tensile strength is excellent, and a filtration filter for separating fine substances, a reaction process or treatment. It can be suitably used for a carrier of a specific participant in the process, an aeration pipe for an aeration tank, a pipe for infiltration of groundwater, a pipe for drainage, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic porous body having a large number of continuous pores and excellent in permeability of various gases and liquids and chemical resistance, and a filtration filter for separating fine substances, The present invention relates to a porous body made of ultra-high molecular weight polyethylene, which can be suitably used for a carrier for a specific participant during a reaction process or a treatment process, an air diffuser pipe for an aeration tank, a pipe for infiltration of groundwater, a pipe for drainage, and the like.

[0002]

2. Description of the Related Art Conventionally, there has been known a porous body obtained by sinter-molding an ultrahigh molecular weight polyethylene simple substance or a composition obtained by mixing it with another resin such as medium molecular weight polyethylene or high density polyethylene.

[0003]

However, in the porous body obtained by sintering and molding the above ultrahigh molecular weight polyethylene simple substance, the average particle diameter of the ultrahigh molecular weight polyethylene which is usually used is about 100 μm, and the average molecular weight is 400x
It has a characteristic that the particle size is about 10 ⁴ , the particle size is fine, and the fluidity during processing is relatively excellent. Such ultra-high molecular weight polyethylene has good processability, but due to the excellent fluidity and fine particle size, the bulk density of the obtained porous body tends to be high and the pressure loss tends to be large.

Further, in a porous body obtained by sintering and molding a mixed composition of ultrahigh molecular weight polyethylene and medium molecular weight polyethylene or high density polyethylene, the average particle diameter of the mixed medium molecular weight polyethylene or high density polyethylene is 20 μm.
m to 80 μm and average molecular weight of 1 × 10 ^{4 to} 5
Since it has a fine particle size of about × 10 ⁴ and is relatively excellent in fluidity, even if an ultrahigh molecular weight polyethylene having a relatively large average particle size is used, the processability and mechanical properties are high. Although the mechanical strength is good, only a porous body having a high bulk specific gravity, that is, a low porosity can be obtained, and there are cases in which it is not suitable for use depending on the application.

[0005]

The present invention has found that the above problems can be solved by using a specific ultra high molecular weight polyethylene resin, and the gist thereof is that the average particle size is 250 μm to 400 μm,
Porous ultra-high-molecular-weight polyethylene characterized in that a cauliflower-like ultra-high-molecular-weight polyethylene resin having a viscosity average molecular weight in the range of 500 × 10 ^{4 to} 650 × 10 ⁴ is formed by sintering to form a large number of continuous pores. On the body.

The ultrahigh molecular weight polyethylene resin used in the present invention must have an average particle size of 250 μm to 400 μm and a viscosity average molecular weight of 500 × 10 ^{4 to} 650 × 10 ⁴ , and each value is measured as follows. It is the numerical value obtained by the method. The average particle size is obtained by measuring the particle size distribution, then plotting the sieve non-passage (% by weight) against the opening (μm) on the normal probability paper, and obtaining the particle size at the time when 50% by weight has not passed. The particle size distribution was measured by sieving with an electromagnetic shaker (PT-E manufactured by Hosokawa Micron), the sieving was performed using a JIS standard sieve (JISZ-8801), and each opening was 1 from the top. , 180μm, 355μ
m, 250 μm, 177 μm, 150 μm, 88 μm,
It is 44 μm. After sufficiently mixing polymer particles (2.5 g) and carbon black powder (0.025 g) to prepare a sample for measurement, the sample adjusted to a vibrating sieve was set on a shaker, and the amplitude was 1.5 mm for 6 minutes. After shaking, the residual polymer weight on each wire mesh is measured. The weight fraction collected by each sieve is determined from the weight collected by each sieve. Weight fraction collected by each sieve = (weight g collected by each sieve g / 2.5 g + 0.025 g) × 100.

The viscosity average molecular weight is ASTMD-1.
[Η] is measured according to 601 and then ASTMD
The molecular weight was calculated according to -4020.

The average particle size measured by the above method is 2
When the particle size is less than 50 μm or the viscosity average molecular weight is less than 500 × 10 ⁴ , the molded porous body has good mechanical strength, but tends to have a high bulk specific gravity, which is not preferable. On the other hand, if the average particle size exceeds 400 μm or the viscosity average molecular weight exceeds 650 × 10 ⁴ , the bulk density of the molded porous body is low, but the mechanical strength tends to decrease, such being undesirable.

Further, the ultrahigh molecular weight polyethylene resin used in the present invention must have a cauliflower shape. The cauliflower shape here is a surface of a cauliflower in which the entire shape is a sphere with some irregularities, and a plurality of fine cracks are formed between the convexes that slightly travel on the surface. The shape is similar to the shape, and as shown in FIG. 1, it can be identified by a photograph magnified about 100 times.

It is essential that the ultrahigh molecular weight polyethylene resin used in the present invention has the above-mentioned requirements, so that when sintered and molded into a porous body, the pore diameter and porosity of the continuous pores thereof. It is presumed that such particles may be suitable for the intended use, and in particular, the irregularities or multiple cracks of the ultra high molecular weight polyethylene resin particles, when the particles are heated, efficiently absorb heat and cracks. It is presumed that the particle size is increased and the particles are easily expanded as a whole, which contributes to lowering the bulk specific gravity of the molded porous body.

Further, among the molding methods described below, in the so-called static molding method, which is a so-called static molding method, the cauliflower-like shape remains relatively after the sintering molding, and the dynamic molding is performed. Even in the lamb extrusion method, which is a type of dynamic molding method, the cauliflower-like shape is destroyed, but it is less affected by the fusion between particles necessary to form continuous pores. The pore diameter and porosity of the pores are
It is speculated that it may be suitable for the application.

The ultrahigh molecular weight polyethylene resin may be used as an additive, for example, as a melting aid in an amount of 5 to 20 parts by weight of a medium molecular weight polyethylene resin, or as a regulator for the porosity and elongation of the porous material. 5 to 20 parts by weight of high density polyethylene resin, medium density polyethylene resin, low density polyethylene resin or medium molecular weight polyethylene resin, and further 0.5 to 10 parts by weight, preferably 1.5 to 2.
5 parts by weight of a conductivity-imparting agent, 0.5 to 10 parts by weight, preferably 5 parts by weight or less of a lubricant, and further 0.003 to 0.
3 parts by weight, preferably 0.01 to 0.15 parts by weight of an organic peroxide or the like may be added.

As the conductivity-imparting agent, Ketjen black, channel black, furnace black,
Thermal black, conductive carbon black such as acetylene black and the like, metal powder, metal oxides and the like, as the lubricant, montanic acid ester wax, there is a wax composed of a fatty acid derivative, and as the organic peroxide, 2,5-dimethyl- (t-butylperoxy) hexane, dicumyl peroxide and the like can be mentioned.

In the present invention, the above-mentioned ultra-high molecular weight polyethylene resin is used for sinter molding, but various sinter molding methods can be used. As a so-called static molding method, which is a so-called static molding method, for example, a molding die including an outer mold having a tubular shape and an inner mold inserted therein is used, and a gap between the outer mold and the inner mold is used. There is a method of heating the molding die after filling the raw material into the cavity formed in the part.

Further, as a method which is a dynamic molding method,
Ram extruding method that uses a ram type extruder that has a piston (also called a plunger) that reciprocates in a temperature-adjustable cylinder that has a mold at the tip, and temperature adjustment that has a mold at the tip Injection molding method using an injection molding machine with a screw built in a cylinder that can be used, and an extrusion molding method using an extrusion molding machine with a screw in the temperature-adjustable cylinder that has a mold at the tip. Using a molding die consisting of a female die and a male die inserted into its inner diameter, using a compression molding machine that heats the molding die after filling the raw material into the cavity formed inside the female die A compression molding method to be performed, a continuous type in which a raw material is extruded into a molding die with a temperature-adjustable cylinder having a molding die composed of a pair of upper and lower moving belts or a lower moving belt at the tip. Continuous pressing process or the like performed using less machine and the like, can be appropriately selected depending on the shape requirements of the static molding or final porous body from the dynamic molding method. In addition, the final shape of the porous body is
A hollow body such as a cylinder, a prism, an ellipse, a rectangle, and a star, or a plate, a rod, a bottomed cylinder, or a dish is appropriately selected depending on its application.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 Average particle size 370 μm, viscosity average molecular weight 58
The cauliflower-like ultra high molecular weight polyethylene resin as shown in FIG. 1 having 0 × 10 ⁴ and a bulk specific gravity of 0.43 is filled in the space between the metal mold having the cylindrical inner mold and the outer mold, and the following molding is performed. Under the conditions, a pipe-shaped porous body was obtained. ◎ Molding conditions Metal tubular mold; Inner mold outer diameter ... 50mm Outer mold inner diameter ... 56mm Temperature / time; 200 ° C x 50 minutes ◎ Porous body shape pipe; Outer diameter: 55mm, Inner diameter: 49mm, Wall thickness: 3mm

(Example 2) The same cauliflower-like ultra high molecular weight polyethylene resin as in Example 1 was used, and a composition in which carbon black was mixed at a ratio of 5% by weight was used to fill a metal cylindrical mold, Under the same conditions as in Example 1, a pipe-shaped porous body was obtained.

(Example 3) The same cauliflower-like ultra-high molecular weight polyethylene resin as in Example 1 was used, and a ram extruder having a cylinder provided with a molding die at the end and a heating mechanism on the outer peripheral surface was used. Then, a pipe-shaped porous body was obtained under the following extrusion conditions. ◎ Extrusion conditions Extrusion rate: 10 kg / hr Orifice; Continuous slit of 1 mm width Molding die: Annular temperature; Chamber ... 170 ° C., Cylinder ... 240 ° C., Molding die ... 200 ° C. Porous body shape pipe; Outer diameter: 56 mm, Inner diameter: 50 mm, wall thickness: 3 mm

(Example 4) Using the same cauliflower-like ultra-high molecular weight polyethylene resin as in Example 1, an injection molding machine (FSK80-UH: made by Komatsu Seisakusho) was used to obtain 60% resin with respect to the mold capacity. A porous body was obtained by injecting. ◎ Injection conditions Injection pressure: 2,030 kg / cm ² Injection temperature: 200 ° C Injection weight: 47 g Mold temperature: 100 ° C Cooling time: 40 seconds ◎ Porous body shape Disc shape: 100 mmφ × 10 mm

(Comparative Example 1) A bulk ultra-high molecular weight polyethylene resin having an average particle diameter of 120 μm, a viscosity average molecular weight of 400 × 10 ⁴ , and a bulk specific gravity of 0.42 was used and filled in a metal cylindrical mold, and an example was obtained. A pipe-shaped porous body was obtained under the same conditions as in 1.

Comparative Example 2 A composition in which an ultrahigh molecular weight polyethylene resin having an average particle diameter of 160 μm and a viscosity average molecular weight of 330 × 10 ⁴ and a high density polyethylene having an average particle diameter of 80 μm are mixed at a ratio of 75:25. The product was filled in a metal tubular mold, and a pipe-shaped porous body was obtained under the same conditions as in Example 1.

Comparative Example 3 A cauliflower-like ultra high molecular weight polyethylene resin having an average particle diameter of 187 μm, a viscosity average molecular weight of 600 × 10 ⁴ , and a bulk specific gravity of 0.38 is provided with a molding die at its end and heated on the outer peripheral surface. The same pipe-shaped porous body was obtained under the same extrusion conditions as in Example 3 using a ram extruder having a cylinder equipped with a mechanism.

Comparative Example 4 A cauliflower-like ultra high molecular weight polyethylene resin having an average particle diameter of 160 μm, a viscosity average molecular weight of 230 × 10 ⁴ , and a bulk specific gravity of 0.45 was prepared under the same molding machine and molding conditions as in Example 4. The same disk-shaped porous body was obtained. Table 1 shows the results of measurements of various physical properties of the porous bodies obtained in Examples 1 to 4 and Comparative Examples 1 to 4. Here, the pressure loss is a value measured at an air flow rate of 1 m / min, and the tensile strength and elongation are numerical values measured according to JIS K7113.

[Table 1]

It can be seen from Table 1 that Examples 1 to 4 have low bulk specific gravity, low pressure loss, and excellent mechanical strength such as tensile strength. On the other hand, in Comparative Example 1 in which the average particle diameter is different from the viscosity average molecular weight and the polymer shape is different, it can be seen that the bulk specific gravity is high and the pressure loss is large. Similarly, the average particle size and viscosity average molecular weight are small,
In Comparative Example 2 in which a high-density polyethylene resin is mixed, and in Comparative Example 3 in which the shape of the polymer used is the same but the average particle size is small, and in Comparative Example 4 in which the polymer shape is the same and the viscosity average molecular weight is small, the bulk specific gravity is further increased. It can be seen that the pressure loss is high and the pressure loss is large.

[0025]

As described above, according to the porous body made of ultra-high molecular weight polyethylene of the present invention, a homogeneous porous body having a low bulk density can be obtained, the pressure loss can be kept low, and the tensile strength and the like can be improved. It has excellent mechanical strength and is suitable for use as filtration filters for separating fine substances, carriers for specific substances involved in the reaction process or treatment process, diffusers for aeration tanks, pipes for infiltration of groundwater or drainage pipes. It can be preferably used.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle structure of an ultrahigh molecular weight polyethylene resin used in the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Masano 2480, Sanchi, Hiratsuka-shi, Kanagawa Mitsubishi Plastics Corporation Hiratsuka factory

Claims (1)

[Claims] 1. An average particle diameter of 250 μm to 400 μm,
Porous ultra-high-molecular-weight polyethylene characterized in that a cauliflower-like ultra-high-molecular-weight polyethylene resin having a viscosity average molecular weight in the range of 500 × 10 ^{4 to} 650 × 10 ⁴ is formed by sintering to form a large number of continuous pores. body.