JPH05470A - Chemical-resistant tube and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a chemical-resistant tube provided with electrification prevention function, without any restrictions in length and composed of inexpensive fluorine resin. CONSTITUTION:A chemical-resistant tube 1 is manufactured by the two-layer tubular extrusion molding and is of double structure consisting of an outer layer 2 composed of perfluoroalkoxyethylene resin and an inner layer 3 composed of perfluoroalkoxyethylene mixed with carbon powder.

Description

Detailed Description of the Invention

[0001]

The present invention relates to chemistry, paints, inks,
TECHNICAL FIELD The present invention relates to a chemical-resistant tube made of a fluorine-based resin used for piping used in production lines in various industrial fields such as industrial chemicals and pharmaceuticals, interior materials for piping, and a method for producing the same.

[0002]

Fluorine-based resins are widely used in various industrial fields because they are excellent in chemical resistance, heat resistance, non-adhesiveness, electrical characteristics and the like. However, when used for chemical resistant tubes such as piping that allows liquid or gas to pass or interior materials for piping,
Since the fluororesin has a high insulating property, the tube itself and the flowing fluid are easily charged, and there is a risk of ignition and explosion due to discharge when handling an organic solvent or flammable gas.

Therefore, conventionally, as a tube using polytetrafluoroethylene (hereinafter abbreviated as PTFE), a conductive inner layer mixed with carbon powder such as carbon black is provided on the inner surface of the tube to prevent static electricity. Things have appeared.

[0004]

[Problems to be Solved by the Invention] However, PTF
The tube using E cannot be manufactured by ordinary extrusion molding, and P is produced by so-called paste extrusion which is a kind of injection molding.
Since a method of injecting a mixed paste of TFE powder and oil into a molding die and heating it is adopted, badge production is poor and manufacturing efficiency is poor, and the length determined by the molding die makes it impossible to obtain a long product. In addition, the material exceeding the actual length of use becomes an unused short material, resulting in a large material loss and is extremely uneconomical.

In view of the above-mentioned circumstances, the present invention provides a chemical resistant tube using a fluororesin, which has an excellent antistatic effect and which is capable of producing a long product by continuous means. To aim.

[Means for Solving the Problems]

In order to achieve the above object, the chemical resistant tube of the present invention employs a constitution comprising an outer layer made of perfluoroalkoxyethylene resin and an inner layer made of carbon powder mixed in the perfluoroalkoxyethylene resin. It was done.

The method for producing the chemical resistant tube of the present invention is a two-layer tubular extrusion molding in which the melt of perfluoroalkoxyethylene resin is on the outside and the melt of perfluoroalkoxyethylene resin mixed with carbon powder is on the inside. ,
It is characterized in that the tube composed of the inner and outer layers is continuously manufactured.

[0008]

[Function] Perfluoroalkoxy ethylene resin (hereinafter,
(Abbreviated as PFA) is a thermoplastic resin having a melting point of 300 to 310 ° C. and has fluidity in a molten state,
It can be formed into a tube by extrusion. Therefore, there is no restriction on the length of the obtained tube.

In the present invention, however, a double-layered tube having an outer layer of PFA and an inner layer of carbon powder mixed with the PFA is formed by coaxial extrusion molding. This double-structured tube has excellent chemical resistance, heat resistance, non-adhesiveness, electrical and mechanical properties derived from PFA, and high antistatic action based on the conductivity of the inner layer containing carbon powder. Indicates.

For the purpose of preventing static electricity, it may be considered that the entire tube has a single layer in which carbon powder is mixed with PFA. However, in such a single layer structure, a large amount of expensive carbon powder is used. In addition to being uneconomical, the mechanical properties such as strength of the entire tube are deteriorated.

[0011]

1 and 2 show a first embodiment of the chemical resistant tube of the present invention. The tube 1 includes an outer layer 2 made of PFA and an inner layer 3 made of PFA containing carbon powder.
It consists of and.

The thickness of the inner layer 3 is preferably 5 to 20% of the outer layer 2. For example, when the tube outer diameter is about 20 to 50 mm, the outer layer 2 is about 1 to 2 mm and the inner layer 3 is about 0.1 to 0.2.
It is usual to set the thickness to about mm.

The content of the carbon powder in the inner layer 3 is preferably in the range of 5 to 20% by weight. If the content is too large, the strength and characteristics of the layer itself are deteriorated and the cost becomes high. Can't exert.

In order to manufacture such a tube 1, a general multi-layer (two layers in this case) extrusion molding machine which has been conventionally used for manufacturing various synthetic resin molded products having a multi-layer structure is used. PFA for outer layer 2 and carbon powder-P for inner layer 3
The FA mixture is melted at about 330 to 360 ° C.,
The former may be concentrically merged so that the former is on the outside and the latter is on the inside by a two-layer tubular extrusion die, and extrusion molding may be performed continuously. As a commercial product of PFA, there is Teflon PFA under the trade name manufactured by EI DuPont. Carbon black is usually used as the carbon powder.

FIG. 3 shows a second embodiment of the chemical resistant tube of the present invention. This tube 4 is composed of an outer layer 2 made of PFA and an inner layer 3 made of PFA containing carbon powder as in the first embodiment, but the outer shape is bellows-like by an uneven spiral 5 and has bendability. It is a so-called flexible type.

In order to obtain such an accordion-like outer shape, the tube 1 having a smooth peripheral surface as in the first embodiment may be heated and softened by secondary processing and embossed. It is possible to apply the uneven spiral 5 directly in the cured state. On the other hand, in the case of PTFE, the above-mentioned secondary processing is indispensable to obtain a tube having a bellows-shaped outer shape.

In the chemical resistant tube of the present invention, various additives such as colorants and fillers may be added to the outer layer 2 and the inner layer 3 if necessary.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, a tube made of a fluororesin having excellent chemical resistance, heat resistance, non-adhesiveness, electrical characteristics, etc. exhibits a sufficient antistatic effect and is restricted in length. It is possible to provide at low cost what can be made into a long product.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a chemical resistant tube according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the tube.

FIG. 3 is a partially cutaway side view of the chemical resistant tube of the second embodiment.

[Explanation of symbols]

1, 4 ... Tube, 2 ... Outer layer, 3 ... Inner layer.

Claims (2)

[Claims] 1. A chemical resistant tube comprising an outer layer made of a perfluoroalkoxyethylene resin and an inner layer having carbon powder mixed in the perfluoroalkoxyethylene resin. 2. A tube comprising inner and outer layers according to claim 1, which is formed by two-layer tubular extrusion molding in which a melt of perfluoroalkoxyethylene resin is on the outside and a melt of perfluoroalkoxyethylene resin mixed with carbon powder is on the inside. A method for producing a chemical resistant tube, which comprises continuously producing.