JP3481346B2 - Method for producing ultra high molecular weight polyethylene porous body - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous body made of ultra-high molecular weight polyethylene, and more particularly to a method for producing a porous body having a large number of continuous pores and having a high permeability and chemical resistance. Ultra-high-molecular-weight polyethylene porous material that can efficiently obtain a long porous material that is used as a filter for fine substances and a carrier for specific substances involved in the reaction or treatment process, etc. And a method for producing the same. [0002] Conventionally, a porous body is continuously formed from ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE") using a ram extruder provided with a breaker plate. It has been proposed. That is, when UHMWPE is charged into a ram extruder and the cylinder temperature of the ram extruder is heat-treated at a temperature not lower than the melting point of UHMWPE and not higher than 300 ° C., UHM
The WPE passes as a rubbery viscous melt through a number of orifices in a breaker plate provided in the ram extruder at a pressure of 4 to 17 kg / cm ² , and the heat and pressure cause the melt fracture to occur. (Phenomenon causing irregular irregularities on the surface of the molded article), or the particles are extruded as strand-like dispersed particles such as those in which the particles are connected in a string form with a high or low bulk density, and subsequently the strand-like dispersed particles are extruded. Was passed through a molding die to fuse the strand-like dispersed particles to each other to form a porous body. However, in the porous body made of UHMWPE obtained by using the above-described ram extruder, a strand pattern generated in the extrusion direction in the form of a stripe appears on the outer surface of the formed porous body. There is a problem that a porous body having a low porosity is formed. In other words, considering that UHMWPE is difficult to flow, the hole diameter of the orifice of the breaker plate to be used is relatively large, and in addition, when a porous body having a high porosity is desired for the molding die, the entrance of the porous body is required. The UHMWPE of the molten strand-like dispersed particles fuses with each other in a state in which the back pressure received is low even when flowing through the mold, since the passage cross sections of the side and the outlet side are set to be substantially the same inner passage. However, as a result, if a back pressure is slightly increased to generate a strand pattern or conversely cancel the strand pattern, a porous body having a relatively low porosity results. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the present invention is to provide an ultra-high molecular weight polyethylene porous material which is formed by extruding ultra-high molecular weight polyethylene with a ram extruder. In the method for producing a solid body, a breaker plate provided with a continuous or discontinuous linear slit corresponding to the cross-sectional shape of the extruded product is provided at a tip portion in a ram extruder, and at least from the linear slit, A composition mainly composed of ultra-high molecular weight polyethylene partially melted is passed at a heating temperature of 150 ° C. to 300 ° C., connected to a breaker plate, and formed into almost the same shape as an extruded product. A method for producing a porous body made of ultra-high molecular weight polyethylene, characterized in that partial melting points are mutually fused in a mold to form a continuous porous body. According to the present invention, a ram extruder is used, and a UHMWPE is formed in a linear slit having a specific shape corresponding to the cross-sectional shape of an extruded product of a breaker plate provided in the extruder.
To make the particulate UHMWPE into a continuous expanded body having a high porosity corresponding to the cross-sectional shape of the extruded product. This is a method for producing a porous body made of UHMWPE, in which the porous body having continuous pores is formed. That is, UHMWPE slightly expands after passing through the linear slit, and has a thickness larger than the width of the linear slit.
It becomes a continuous expanded body with a high porosity almost in the shape corresponding to the desired final molded article, and immediately after passing through the slit, in the molding die, at a pressure such that the pores of the expanded body are not crushed, the shape of the desired final molded article It is shaped. The linear slits are provided in a continuous or discontinuous shape having substantially the same shape as the cross-sectional shape of the extruded product, and the width and the like of the slit can be appropriately determined according to the cross-sectional shape of the extruded product. At this time, in order to obtain a homogeneous porous body having a bulk density of 0.80 g / cm ³ or less, UHMWPE must be treated in a selected shear rate region, for example, 1 × 10 ¹ to 1 × 10 3.
It is preferable to pass through the linear slit of the breaker plate at ⁴ sec ^-1 . In the production method of the present invention, unlike the prior art, since the breaker plate does not have a large number of orifices, a strand pattern caused by the orifice does not occur on the surface of the porous body, and a uniform porous body having a low bulk density is produced. Can be molded. [0010] The above UHMWPE may be added with 5 to 20 parts by weight of a medium molecular weight polyethylene as a melting aid, or with 5 to 20 parts by weight as a modifier of porosity and elongation of a porous body. -Medium / low density polyethylene, medium high molecular weight polyethylene, etc. can be added. Furthermore, 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, 0.003 to 0.3 parts by weight, preferably 0.01 to 0.15 parts by weight of an organic peroxide and the like Can also be added. Examples of the conductivity-imparting agent include conductive carbon black such as Ketjen black, channel black, furnace black, thermal black, and acetylene black, metal powders, metal oxides, and the like. Examples of the organic peroxide include 2,5-dimethyl-2,5- (t-butylperoxy) hexane and dicumyl peroxide. Hereinafter, the present invention will be described with reference to examples. EXAMPLES Example 1 Viscosity average molecular weight 600 × 10 ⁴ , average particle size 187 μm,
UHMWPE having a bulk specific gravity of 0.377 and an elastic modulus at 200 ° C. of 4.15 × 10 ⁷ dyne / cm ²
Using a ram extruder equipped with a cylindrical molding die, the shear rate at the linear slit of the breaker plate was set to 4.1 × 10 ³ sec ⁻¹ (the shape of the linear slit = outer diameter of 56. 7 mm, inner diameter 56.3 mm, slit width 0.2 mm), outer diameter 60 mm, inner diameter 53 m
A pipe-shaped porous body having a thickness of 3.5 mm and a thickness of 3.5 mm was extruded. * Extrusion conditions Extrusion amount: 14 kg / hr Temperature: chamber: 170 ° C., cylinder: 240
° C, Mold: 190 ° C Example 2 Viscosity average molecular weight 330 × 10 ⁴ , average particle size 335 μm,
UHMWPE having a bulk specific gravity of 0.458 and an elastic modulus at 200 ° C. of 3.50 × 10 ⁷ dyne / cm ²
3. Using the same ram extruder and extrusion conditions as in Example 1 above, set the shear rate at the linear slit of the breaker plate to 4.
1 × 10 ³ sec ⁻¹ (shape of linear slit = outer diameter 5
6.7mm, inner diameter 56.3mm, slit width 0.2m
m), outer diameter 60 mm, inner diameter 53 mm, wall thickness 3.
A 5 mm pipe-shaped porous body was extruded. Example 3 A viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 160 μm,
UHMWPE having a bulk specific gravity of 0.449 and an elastic modulus at 200 ° C. of 3.75 × 10 ⁷ dyne / cm ² ,
3. Using the same ram extruder and extrusion conditions as in Example 1 above, set the shear rate at the linear slit of the breaker plate to 4.
1 × 10 ³ sec ⁻¹ (shape of linear slit = outer diameter 5
6.7mm, inner diameter 56.3mm, slit width 0.2m
m), outer diameter 60 mm, inner diameter 53 mm, wall thickness 3.
A 5 mm pipe-shaped porous body was extruded. Example 4 A viscosity average molecular weight of 600 × 10 ⁴ , an average particle size of 187 μm,
UHMWPE having a bulk specific gravity of 0.377 and an elastic modulus at 200 ° C. of 4.15 × 10 ⁷ dyne / cm ²
Using the same ram extruder and extrusion conditions as in Example 1, the shear rate at the linear slit of the breaker plate was set to 3.
6 × 10 ¹ sec ⁻¹ (shape of linear slit = outer diameter 5
8.5mm, inner diameter 54.5mm, slit width 2.0m
m), outer diameter 60 mm, inner diameter 53 mm, wall thickness 3.
A 5 mm pipe-shaped porous body was extruded. Example 5 A viscosity average molecular weight of 330 × 10 ⁴ , an average particle size of 335 μm,
UHMWPE having a bulk specific gravity of 0.458 and an elastic modulus at 200 ° C. of 3.50 × 10 ⁷ dyne / cm ²
Using the same ram extruder and extrusion conditions as in Example 1, the shear rate at the linear slit of the breaker plate was set to 3.
6 × 10 ¹ sec ⁻¹ (shape of linear slit = outer diameter 5
8.5mm, inner diameter 54.5mm, slit width 2.0m
m), outer diameter 60 mm, inner diameter 53 mm, wall thickness 3.
A 5 mm pipe-shaped porous body was extruded. Example 6 A viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 160 μm,
UHMWPE having a bulk specific gravity of 0.449 and an elastic modulus at 200 ° C. of 3.75 × 10 ⁷ dyne / cm ² ,
Using the same ram extruder and extrusion conditions as in Example 1, the shear rate at the linear slit of the breaker plate was set to 3.
6 × 10 ¹ sec ⁻¹ (shape of linear slit = outer diameter 5
8.5mm, inner diameter 54.5mm, slit width 2.0m
m), outer diameter 60 mm, inner diameter 53 mm, wall thickness 3.
A 5 mm pipe-shaped porous body was extruded. Comparative Example 1 A viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 160 μm,
UHMWPE having a bulk specific gravity of 0.449 and an elastic modulus at 200 ° C. of 3.75 × 10 ⁷ dyne / cm ² ,
Under the same extrusion conditions as in Example 1, a breaker plate provided with a plurality of orifices instead of the linear slits was used, and the shear rate was 4.0 × 10 ² sec ⁻¹ (orifice... 1.0 mmφ × 5.0 mmL). , Number of holes: 72), and a pipe-shaped porous body having the same size as in the above example was extruded. Table 1 shows the bulk specific gravity measured for the porous bodies obtained in Examples 1 to 6 and Comparative Example 1. [Table 1] From Table 1, all of the porous bodies obtained in Examples 1 to 6 have low bulk specific gravities and achieve the intended purpose, and have no strand pattern on the outer surface. The appearance was good. On the other hand, the porous body obtained in Comparative Example 1 had a high bulk specific gravity and generated a strand pattern. The present invention has the above-mentioned structure, and can exhibit the following effects. That is, according to the present invention, UHM
By passing WPE through the linear slits of the breaker plate, it is possible to obtain a porous body having continuous pores having a lower bulk density, and a large and uniform porosity, and a strand pattern on the porous body surface. Not the desired UH
The MWPE porous body can be easily and continuously formed in a short time.

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Claims (1)

(57) [Claim 1] In a method for producing a porous body made of ultra-high molecular weight polyethylene by extruding ultra-high molecular weight polyethylene with a ram extruder, an extruded product is formed at the tip of the ram extruder. Arrange a breaker plate provided with a continuous or discontinuous linear slit corresponding to the cross-sectional shape, from the linear slit, at least a part of a composition mainly composed of ultra-high molecular weight polyethylene in a molten state At a heating temperature of 150
Passed in the range of ℃ ~ 300 ℃, connected continuously to the breaker plate, in a molding die almost the same shape as the extruded product, partially fused parts are mutually fused to form a continuous porous body A method for producing a porous body made of ultra-high molecular weight polyethylene.