JPH0752263A - Molding method for plastic porous cylindrical body - Google Patents

Abstract

PURPOSE:To obtain a method for molding a sintered porous cylindrical body made of a thermoplastic with an air permeability. CONSTITUTION:A composition mainly composed of at least one kind of plastic selected out of a low- or high-density polyethylene, an ultra-high-molecular- weight polyethylene, a polypropylene, an ethylene-vinyl acetate copolymer, and others is charged into a space of a double cylindrical molding die. The double cylindrical molding die is put in a heating furnace set to a temperature that is not lower than the melting temperature of the composition or high enough to partially melt the composition and sintered while being rotated on its own axis by a continuously moving device. Thereafter, the molding die is transferred to a cooling tank and cooled to an ordinary temperature. In this manner, a sintered porous cylindrical body having a good quality in appearance and keeping a uniform quality can be obtained with a high productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a sintered porous cylindrical body having an air permeability and made of a thermoplastic (hereinafter referred to as "plastic").

[0002]

2. Description of the Prior Art Sintered porous molded articles made of plastic having air permeability have hitherto been used as filter materials, adsorbent materials,
Normally used for sound absorbing materials, heat insulating materials, etc., this molded body uses a mold having a molding space of a desired shape, and a plastic such as ultra high molecular weight polyethylene is filled in the molding space of the mold, Molded by a batch type sintering molding method, in which it is heated in the mold with or without pressure, heated at a temperature above the melting point of the plastic or partially melted for a predetermined time, sintered, and then taken out from the mold. It is known to be done.

However, in the above batch type sintering molding method, the heating temperature, the heating time or the cooling temperature suitable for the molding conditions, that is, the type of resin used, the particle size of the plastic, the particle size distribution, the molecular weight, the composition, the mold filling amount, etc. Since it is necessary to adjust the cooling time and the like to each mold, there are problems that productivity is low and it is difficult to maintain uniform quality.

On the other hand, a ram type extruder equipped with a die having a predetermined shape at the tip is used to fill a thermoplastic resin into a cylinder heated to a predetermined temperature and sinter in the cylinder while extruding at a predetermined pressure. An extrusion type sinter molding method for cooling and molding this is known. In the molding method, a sintered porous cylindrical body having fine and uniform air permeability that can be used for the above-mentioned filter material and the like is obtained. Molding is difficult.

[0005]

Means for Solving the Problems The present invention is to solve the above-mentioned problems, and the gist thereof is low-density to high-density polyethylene, ultra-high-molecular-weight polyethylene, polypropylene,
A composition mainly composed of one or more plastics selected from ethylene-vinyl acetate copolymer and the like is filled in a gap of a double-cylinder molding die, and the double-cylinder molding die is melted at a temperature not lower than the melting temperature of the composition. Alternatively, it is placed in a heating furnace set to a temperature at which it partially melts, is sintered while rotating by a continuous moving device, is then transferred to a cooling tank, and is cooled to room temperature. Is the way.

The present invention is a method for molding a plastic porous cylindrical body (hereinafter referred to as "cylindrical body") comprising the following steps. (1) A composition mainly composed of a plastic selected from low density to high density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene-vinyl acetate copolymer, etc. (2) A heating furnace in which the mold is set to a temperature above the melting temperature of the filled composition or to a temperature at which the composition partially melts while moving while rotating the mold while standing on a continuous moving device. (3) The composition filled in the molding die is heated to a temperature equal to or higher than the melting temperature or a temperature at which the composition partially melts, and the composition is melted to partially leave the plastics together to leave voids between the resin layers. Step of welding (4) Next, while rotating and moving the mold, the mold is placed in a cooling tank adjacent to the superheating furnace and cooled to almost room temperature, and subsequently a molded cylindrical body is formed. A step of releasing from the mold, consisting of, or the like.

The plastic used in the present invention is low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, ethylene-vinyl acetate copolymer and the like, and one or two of these resins are used. A mixture of the above is used, but a combination of ultrahigh molecular weight polyethylene and low density polyethylene or a combination of high density polyethylene and ethylene-vinyl acetate copolymer is preferable.

In the above composition, one or more additives such as a cross-linking agent, a lubricant and a conductivity-imparting agent may be blended with the plastic as the main component. The cross-linking agent is 2,5-dimethyl-2,5- (t-butylperoxy) hexane, dicumyl peroxide, etc., and is added in an amount of 0.004 to 0.2 parts by weight based on 100 parts by weight of the plastic. , And preferably 0.012 to 0.12 parts by weight. The lubricant is a montanic acid ester wax, a wax of a fatty acid derivative, or the like, and the addition amount is 0.5 to 10 parts by weight, preferably 5 parts by weight or less with respect to 100 parts by weight of the plastic. The conductivity-imparting agent is carbon black or graphite, and carbon black is Ketjen black, channel black, furnace black,
Thermal black, acetylene black, etc. are added in an amount of 1.0 to 5.3 with respect to 100 parts by weight of plastic.
Parts by weight, preferably 1.5 to 2.6 parts by weight.

The heat treatment in the present invention does not heat the entire plastic to the extent of melting, but when one kind of plastic is used, the surface of the particles of the plastic is melted but not inside. It is in a state where the core of melting exists, and heating may be performed to such an extent as to cause partial fusion with the adjacent plastic particles.

The double-cylinder molding die used in the present invention is composed of a male die and a female die, and the male die has almost the same inner surface shape or inner diameter as that of the cylindrical body to be sintered. The female mold has the same shape or size, and the female mold has substantially the same shape or size as the outer shape or outer diameter of the cylindrical body to be sintered. Then, when the male die is inserted into the female die, a gap having a predetermined shape or size is formed between the inner surface of the female die and the outer surface of the male die, and the raw material composition is present in this gap. Is filled in, and becomes a thick part of the tubular molded product after sintering.

The double-cylinder forming die is a double-cylinder which is heated for a predetermined time by being heated by a chain while being rotated by a chain while being kept standing on a continuous moving device having a caterpillar body and an endless belt. While the mold continues to rotate and move, it is placed in a water-cooled or air-cooled cooling tank adjacent to the heating furnace, cooled to almost room temperature, and then the tubular body is released from the double-tube mold.

[0012]

[Example 1] 97.5 wt% of ultra high molecular weight polyethylene
And 2.5% by weight of carbon black are mixed to obtain a raw material composition, and 50 g of the raw material composition has an outer diameter of 50 mm and an inner diameter of 4
38m outside diameter in a 4mm, 300mm long female mold
A male mold having a diameter of m, an inner diameter of 32 mm and a length of 500 mm was inserted and filled in a double-cylinder forming die having a gap of about 3 mm (filling space of about 115 cm ³ ) while applying vibration. Then, the double-cylinder molding die was rotated at 10 rpm in a heating furnace whose temperature was controlled at 200 ° C., and was erected on a caterpillar body moving at a speed of 6 cm / min for sintering for 60 minutes. Subsequently, the double-cylinder molding die was placed in a shower water-cooling type cooling tank, cooled for 1 minute while rotating and moving, and then released from the mold to form a porous cylinder having an outer diameter of 43 mm, an inner diameter of 37 mm, and a length of 290 mm with good appearance. A molded body was obtained.

[0013]

Example 2 Ultra-high molecular weight polyethylene 87.5 wt%,
Low-density polyethylene (10 wt%) and carbon black (2.5 wt%) were mixed to obtain a raw material composition, and the raw material composition 5
Using 0 g of the same double-cylinder molding die and heating furnace as in Example 1, a cylindrical molded article having an outer diameter of 43 mm, an inner diameter of 37 mm, and a length of 290 mm and having good appearance quality was produced under the same sintering molding conditions. Obtained.

[0014]

Since the present invention has the above-mentioned configuration, it has the following effects. That is, according to the present invention, a sintered porous cylindrical body having good appearance quality and uniform quality can be obtained with high productivity.

Claims (1)

[Claims] 1. A composition of a double-cylinder molding die containing a composition mainly composed of one or more plastics selected from low-density to high-density polyethylene, ultra-high-molecular-weight polyethylene, polypropylene, ethylene-vinyl acetate copolymer and the like. Filled in, and put the double-cylinder molding die in a heating furnace set to a temperature above or above the melting temperature of the composition or to a temperature at which it partially melts, and sinters while rotating on a continuous moving device, then transfers to a cooling tank. A method of molding a plastic porous cylindrical body, which comprises cooling to room temperature by heating.