JP3483331B2 - Method for producing porous body made of ultra-high molecular weight polyethylene - 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 permeability and chemical resistance. The present invention relates to a method for producing a long ultra-high molecular weight polyethylene porous body, which is used as a filter for filtering a fine substance or a carrier of a specific substance in a reaction process or a treatment process. 2. Description of the Related Art Conventionally, ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE") is continuously formed into a porous body by using a ram extruder provided with a breaker plate. It has been proposed to. That is, UHMW
When PE is charged into the ram extruder and the cylinder temperature of the ram extruder is heat-treated at a temperature of not less than the melting point of UHMWPE and not more than 300 ° C., UHMWPE becomes a rubbery viscous melt and is disposed in the ram extruder Through the orifice of the breaker plate at a pressure of 4 to 17 kg / cm ² ,
As strand-dispersed particles such as those that have caused melt fracture (a phenomenon that irregular irregularities are formed on the surface of a molded product) due to the heat and pressure, or those in which the particles are connected in a string form with a high or low bulk density. It was extruded, and subsequently, the strand-like dispersed particles were passed through a molding die to fuse the strand-like dispersed particles to each other to form a porous body. [0003] However, in the porous body made of UHMWPE obtained by using the above-mentioned 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, or A porous body having a relatively low porosity may be formed. That is, in consideration of the difficulty of flowing UHMWPE, the hole diameter of the orifice of the breaker plate to be used is relatively large. Since the passage cross section on the outlet side is set to be substantially the same inner passage, the UHMWPE of the molten strand-like dispersed particles fuse with each other in a state where the back pressure received even when flowing through the molding die is low. 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. In addition to the above-mentioned ram extrusion method, UHMWPE is injected into the cavity of the injection mold at a shear rate of 3.0 × 10 ⁴ sec ⁻¹ or 5.0 ×.
After injection at 10 ⁴ sec ⁻¹ or more, it has been proposed to compress the cavity volume by a specific amount to form a porous body. [0005] That is, in the case of injecting UHMWPE in the form of fine particles at a specific shearing rate, molten plasticized UHMWPE is used.
PE is sprayed into the cavity of the injection mold in the form of a mist,
It is injected as a fine powder or flocculent dispersion in the state of melt plasticization, and this powdery or flocculent dispersion is fused together in the cavity and assembled to form a continuous vent. In order to adjust the degree of coarseness / density (bulk density) of the continuous air holes, the injection amount of the dispersion injected into the cavity is adjusted, or the cavity is compressed after the injection. And so on. [0006] However, although the porous body made of UHMWPE obtained by the above-mentioned injection molding can be formed into a relatively complicated shape, the aggregate of UHMWPE is relatively sparse. In addition, molded articles after cooling are still brittle. In addition, since it is injection molding, there is a problem that it is extremely difficult to form an endless and continuous long object inevitably. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the present invention is that an elastic modulus at 200 ° C. is not less than 1.0 × 10 ⁷ dyne / cm ² , A method for producing a porous body made of UHMWPE, wherein a UHMWPE having a viscosity-average molecular weight of 300 × 10 ⁴ or more is extruded by a ram extruder, comprising a breaker plate having a plurality of orifices disposed at a tip end in the ram extruder. UHMWPE at least partially melted from orifice
Is passed under a condition of a heating temperature of 150 to 250 ° C. and a shear rate of 1.0 × 10 ^{3 to} 3.0 × 10 ⁴ sec ⁻¹ , and is formed continuously with a breaker plate. A method for producing a porous body made of UHMWPE, characterized in that partial melting points are mutually fused in a mold to form a continuous porous body. [0008] The present invention relates to a method for preparing a particulate U having specific characteristic values.
Using HMWPE, a ram extruder is used to reduce the orifice of the ram extruder to a specific shear rate range of 1.0 × 10 ^{3 to} 3.0.
After passing under the conditions of × 10 ⁴ sec ⁻¹ , the particulate UHMWPE is converted into a particulate dispersion or a bulk dispersion in which the particulate UHMWPE is aggregated, and then the porous UHMWPE is transformed into a porous body having a large number of continuous pores. This is a method for producing a UHMWPE porous body to be formed. The UHMWPE used in the present invention cannot be flowed under a low shear stress, such as when measuring the MI value (melt index), or becomes a rubber-like elastic body in a temperature range above the melting point. And its flow behavior is different from that of general-purpose polyethylene and the like. UHMWPE which becomes a rubber-like elastic body in the temperature range above the melting point,
It shows an elastic modulus of 1.0 × 10 ⁷ dyne / cm ² or more at 200 ° C. (ISO / CD6721-7, elastic modulus by a torsion measurement method), and has an average molecular weight of 300 by a viscosity method.
It is in the form of fine powder having a particle size of at least 10 ⁴ and an average particle size of 50 to 400 μm. The UHMWPE may contain 5 to 20 parts by weight of a medium-molecular-weight polyethylene as a melting aid, or 5 to 20 parts by weight of a medium having a high, medium or low content as a regulator of porosity and elongation of a porous body. High-density polyethylene or other medium-density polyethylene can be added. Further, 0.5 to 10 parts by weight, preferably 1.5 to 2.5 parts by weight of a conductivity-imparting agent,
10 parts by weight, preferably 5 parts by weight or less of lubricant, 0.00
3 to 0.3 parts by weight, preferably 0.01 to 0.15 parts by weight, of an organic peroxide or the like can be added. Examples of the conductivity-imparting agent include conductive carbon black and metal powder such as kecken black, channel black, furnace black, thermal black, and acetylene black;
Examples of the lubricant include montanic acid ester waxes and fatty acid derivative waxes, and examples of the organic peroxide include 2,5-dimethyl-2,5- (t-butyl). Peroxy) hexane, dicumyl peroxide and the like. When the rubber-like elastic body is extruded from an orifice of a ram extruder, the orifice is moved to a specific shear rate range of 1.0 × 10 ^{3 to} 3.0 × 10 ⁴ sec.
^-1 range, the UHM melted in the orifice
The rubber-like elastic body of WPE is extruded in the form of particles or a massive dispersion in which the particles are extremely loosely assembled, and these are fused together in a molding die connected to a breaker plate. Thus, a porous body having a favorable outer surface and a desired shape can be easily formed without generating a strand pattern. When the rubber-like elastic body is below the above-mentioned shear rate range, for example, 2.0 × 10 ² sec ⁻¹ or more and 1.0 × 10 2
^When passed through the orifice in less than ³ sec- ¹ , the form of UHMWPE emerging from the orifice becomes strand-shaped dispersed particles such as those that cause melt fracture or that have high or low bulk density and are string-like. Extruded,
When these are fused together in a molding die, a strand pattern is generated on the outer surface of the molded porous body, and the rubber-like elastic body exceeds the above-mentioned shear rate range. At shear rates above 3.0 × 10 ⁴ sec ⁻¹ ,
It is extremely difficult to continuously obtain a good porous body under the current conditions. EXAMPLE 1 UH having a viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 160 μm, a bulk specific gravity of 0.449 and an elastic modulus at 200 ° C. of 3.75 × 10 ⁷ dyne / cm ² .
The shear rate at the orifice of the breaker plate was set to 3.0 × 10 ³ sec ⁻¹ (orifice... 0.5 mmφ × 5. MWPE) using a ram extruder equipped with a cylindrical molding die under the following extrusion conditions. 0 mmL, number of holes: 72)
, 60mm outside diameter, 53mm inside diameter, 3.5m wall thickness
m was extruded. * Extrusion conditions • Maximum extrusion capacity: 15 kg / hr • Extrusion amount: 10 kg / hr • Temperature: Chamber: 170 ° C, Cylinder: 20
0 ° C. and 230 ° C. Mold: 200 ° C. and 230 ° C. Example 2 Viscosity average molecular weight: 600 × 10 ⁴ , average particle size: 187 μm, bulk specific gravity: 0.377, and elastic modulus at 200 ° C. 4.15 × 10 ⁷ dyne / cm ² UH
The shear rate at the orifice of the breaker plate was set to 3.0 × 10 ³ sec ⁻¹ (orifice... 0.5) using the same ram extruder and the same extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 72), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 3 UH having a viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 335 μm, a bulk specific gravity of 0.458, and an elastic modulus at 200 ° C. of 3.50 × 10 ⁷ dyne / cm ² .
The shear rate at the orifice of the breaker plate was set to 3.0 × 10 ³ sec ⁻¹ (orifice... 0.5 mm) by using the same extruder and the same extrusion conditions as in Example 1 above.
φ × 5.0 mmL, number of holes: 72)
A pipe-shaped porous body having the same size as in Example 1 was extruded. Example 4 UH having a viscosity average molecular weight of 440 × 10 ⁴ , an average particle size of 208 μm, a bulk specific gravity of 0.353, and an elastic modulus at 200 ° C. of 6.49 × 10 ⁷ dyne / cm ² .
The shear rate at the orifice of the breaker plate was set to 3.0 × 10 ³ sec ⁻¹ (orifice... 0.5) using the same ram extruder and the same extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 72), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 5 UH having a viscosity average molecular weight of 500 × 10 ⁴ , an average particle diameter of 163 μm, a bulk specific gravity of 0.466, and an elastic modulus at 200 ° C. of 4.23 × 10 ⁷ dyne / cm ² .
The shear rate at the orifice of the breaker plate was set to 3.0 × 10 ³ sec ⁻¹ (orifice... 0.5) using the same ram extruder and the same extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 72), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 6 UH having a viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 160 μm, a bulk specific gravity of 0.449, and an elastic modulus at 200 ° C. of 3.75 × 10 ⁷ dyne / cm ² .
The shearing rate at the orifice of the breaker plate was set to 2.5 × 10 ⁴ sec ⁻¹ (orifice... 0.5) using the MWPE and the same ram extruder and extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 10), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 7 UH having a viscosity average molecular weight of 600 × 10 ⁴ , an average particle size of 187 μm, a bulk specific gravity of 0.377, and an elastic modulus at 200 ° C. of 4.15 × 10 ⁷ dyne / cm ² .
The shearing rate at the orifice of the breaker plate was set to 2.5 × 10 ⁴ sec ⁻¹ (orifice... 0.5) using the MWPE and the same ram extruder and extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 10), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 8 UH having a viscosity average molecular weight of 330 × 10 ⁴ , an average particle diameter of 335 μm, a bulk specific gravity of 0.458, and an elastic modulus at 200 ° C. of 3.50 × 10 ⁷ dyne / cm ² .
The MWPE was subjected to a ram extruder and a ram extruder under the same ram extruder and extrusion conditions as in Example 1 described above, and the shear rate at the orifice of the breaker plate was set to 2.5 × 10 ⁴ sec ⁻¹ (orifice... 0.5 mmφ × 5.0 mmL, The number of holes was set to 10), and a pipe-shaped porous body having the same size as in Example 1 was extruded. EXAMPLE 9 UH having a viscosity average molecular weight of 440 × 10 ⁴ , an average particle size of 208 μm, a bulk specific gravity of 0.353, and an elastic modulus at 200 ° C. of 6.49 × 10 ⁷ dyne / cm ² .
The shearing rate at the orifice of the breaker plate was set to 2.5 × 10 ⁴ sec ⁻¹ (orifice... 0.5) using the MWPE and the same ram extruder and extrusion conditions as in Example 1 above.
mmφ × 5.0 mmL, number of holes: 10), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Example 10 U having a viscosity average molecular weight of 550 × 10 ⁴ , an average particle size of 163 μm, a bulk specific gravity of 0.466, and an elastic modulus at 200 ° C. of 4.23 × 10 ⁷ dyne / cm ² .
The shearing rate at the orifice of the breaker plate was set to 2.5 × 10 ⁴ sec ⁻¹ (orifice... 0.) using the HMWPE with the same ram extruder and extrusion conditions as in Example 1 above.
5 mmφ × 5.0 mmL, the number of holes: 10), and a pipe-shaped porous body having the same size as in Example 1 was extruded. Comparative Example 1 Using the same UHMWPE and ram extruder as in Example 1, under the same extrusion conditions, the shear rate at the orifice of the breaker plate 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. Comparative Example 2 Using the same UHMWPE and ram extruder as in Example 2, under the same extrusion conditions, the shear rate at the orifice of the breaker plate was set in the same manner as in Comparative Example 1, and the size was the same as in the above Example. Was extruded. Comparative Example 3 Using the same UHMWPE and ram extruder as in Example 3, under the same extrusion conditions, the shear rate at the orifice of the breaker plate was set in the same manner as in Comparative Example 1, and the size was the same as in the above Example. Was extruded. Comparative Example 4 Using the same UHMWPE and ram extruder as in Example 4, under the same extrusion conditions, the shear rate at the orifice of the breaker plate was set in the same manner as in Comparative Example 1, and the same size as in the above Example was used. Was extruded. Comparative Example 5 Using the same UHMWPE and ram extruder as in Example 5, under the same extrusion conditions, the shear rate at the orifice of the breaker plate was set in the same manner as in Comparative Example 1, and the same size as in the above Example was used. Was extruded. The porous bodies obtained in Examples 1 to 10 and Comparative Examples 1 to 5 are comparatively shown in Table 1 below. [Table 1] Each of the porous bodies obtained in Examples 1 to 10 has a low bulk specific gravity and achieves the intended purpose, and has a good external appearance without any strand pattern or the like on the outer surface. there were. On the other hand, the porous body obtained in the comparative example had a high bulk specific gravity, a strand pattern was observed on the outer surface, and the appearance quality was poor. The present invention has the above-described structure and has the following effects. That is, according to the present invention, by forming at a shear rate in a specific range, a porous body having continuous pores having a lower bulk specific gravity can be obtained, and the pore porosity is large and uniform, and a strand is formed on the surface of the porous body. A desired UHMWPE porous body having no pattern can be easily formed continuously and in a short time.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-240043 (JP, A) JP-A-60-10021 (JP, A) JP-A-5-21050 (JP, A) JP-A 57- 133039 (JP, A) JP-A-59-19132 (JP, A) JP-A-6-212006 (JP, A) JP-A-5-9332 (JP, A) JP-A-3-178418 (JP, A) 60-15019 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 47/00-47/96

Claims (1)

(57) [Claims 1] An elastic modulus of 1.0 × 10 at 200 ° C.
⁷ dyne / cm ² or more and viscosity average molecular weight of 3
A method for producing an ultra-high molecular weight polyethylene porous body by extruding an ultra-high molecular weight polyethylene of 00 × 10 ⁴ or more with a ram extruder, wherein a plurality of orifices disposed at a tip end in the ram extruder are formed. From the orifice of the breaker plate having at least a portion of a composition mainly composed of ultra-high molecular weight polyethylene in a molten state, a heating temperature of 15%
A shear rate of 1.0 × 10 ^{3 to} 3.0 × 1 at 0 to 250 ° C.
An ultra-high molecular weight polyethylene, which is passed under a condition of 0 ⁴ sec ⁻¹ and is partially fused to each other in a molding die connected to the breaker plate to form a continuous porous body. A method for producing a porous body.