JPH0592531A - Chemical-resistant tube and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a chemical-resistant tube of fluorine resin which is superior in the prevention effect of charging and can produce a continuous material by a continuous means and also can be used in the case where a fluid flowing through the inside extremely disagrees to the mixture of impurities and can be applied for the prevention of charging on the outer face side of pipings or shafts disposed inside a column and a tank. CONSTITUTION:A chemical-resistant tube 1 is constituted of an inner layer 2 of thermoplastic fluorine resin and an outer layer 3 composed of the fluorine resin 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 fluororesin which is used for pipes used for production lines in various industrial fields such as industrial chemicals, pharmaceuticals and semiconductors, interior and exterior materials for pipes, exterior materials for shafts, etc., 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 contact 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]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The tube using E cannot be manufactured by ordinary melt extrusion molding, and by so-called paste extrusion which is a kind of injection molding,
Since a preform of a mixed paste of PTFE powder and dust cut oil is extruded by a molding machine at a temperature below the melting point to evaporate the lubricating oil, and then superheated to a temperature above the melting point of PTFE, a badge production and And production efficiency is poor,
Since the length was determined by the molding die, a long product could not be obtained, and the length exceeding the actually used length became an unused short material, resulting in a large material loss and was very uneconomical.

On the other hand, in the tube whose inner layer side is a conductive layer containing carbon powder as described above, when a fluid is passed inside as a pipe, a trace amount of carbon powder may be separated and mixed into the fluid. For example, it cannot be used for various fluids used in the manufacturing process of electronic parts such as semiconductors that are extremely reluctant to mix impurities, and it also comes into contact with fluids such as pipes and shafts arranged inside tower tanks and tanks. It is unsuitable for equipment where the prevention of static electricity on the outer surface side is important.

In view of the above-mentioned circumstances, the present invention is a chemical resistant tube using a fluororesin, which has an excellent antistatic effect, can manufacture a long product by continuous means, and can be passed inside. It is an object of the present invention to provide a material that can be used even when a fluid is extremely disliked by the inclusion of impurities, and that can be applied to prevent static electricity on the outer surface side of pipes, shafts, etc. arranged inside a tower tank or tank.

[0007]

In order to achieve the above object, the chemical resistant tube of the present invention comprises an inner layer made of a thermoplastic fluororesin and an outer layer obtained by mixing carbon powder with the fluororesin. The following configuration is adopted.

The method for producing the chemical resistant tube of the present invention is a two-layer tubular extrusion molding in which the melt of the thermoplastic fluororesin is on the inside and the melt of the thermoplastic fluororesin mixed with carbon powder is on the outside. The tube made of the inner and outer layers according to claim 1 is continuously manufactured.

[0009]

The thermoplastic fluororesin used in the present invention has fluidity in a molten state, so that it can be molded into a tube by extrusion molding. Therefore, there is no restriction on the length of the obtained tube.

In the present invention, however, a double-layered tube having an inner layer of a thermoplastic fluororesin and an outer layer obtained by mixing carbon powder into the thermoplastic fluororesin is formed by coaxial extrusion molding. This double structure tube has excellent chemical resistance, heat resistance, non-adhesiveness, electrical and mechanical properties derived from thermoplastic fluororesin, and is based on the conductivity of the outer layer containing carbon powder. Has a high antistatic effect.

[0011] Therefore, this tube is a pipe which is placed in contact with a fluid inside equipment such as a column tank or a tank used for reaction, mixing, storage, etc., where external charge prevention is important, and its exterior. It can be suitably used as an exterior material for shafts such as materials and stirrers.

Further, the tube can be used as a pipe for passing a fluid inside or as an interior material thereof, even though the outer layer side is a conductive layer. That is, although the fluororesin is known to have a very high insulating property,
In fact, it has been reported that charge transfer is likely to occur inside the tube due to the influence of ultraviolet rays and the like, and it has been confirmed that this tube also removes the charge in the inner layer through the conductive outer layer by the same phenomenon. Therefore, if this tube is used as a pipe or an interior material for circulating what is extremely disliked by the mixing of impurities such as various fluids used in the manufacturing process of electronic components such as semiconductors, there is a risk of mixing impurities. It is possible to prevent static electricity in a non-existent form.

It should be noted that it is conceivable that the entire tube has a single layer in which carbon powder is mixed in a thermoplastic fluororesin for the purpose of simply preventing static electricity. However, in such a single layer structure,
The amount of expensive carbon powder used becomes very large, which is uneconomical, and the mechanical properties such as strength of the entire tube deteriorate.

[0014]

1 and 2 show a first embodiment of the chemical resistant tube of the present invention. This tube 1 is composed of an inner layer 2 made of a thermoplastic fluororesin and an outer layer 3 made of a fluorocarbon resin containing carbon powder.

The thickness of the outer layer 3 is preferably 5 to 20% of that of the inner layer 2. For example, when the tube outer diameter is about 20 to 50 mm, the inner layer 2 is about 1 to 2 mm and the outer 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 outer layer 3 is preferably in the range of 1 to 10% by weight. When the content is too large, the strength and extrusion characteristics of the layer itself are deteriorated and the cost becomes high. Cannot exert preventive action.

In order to manufacture such a tube 1, a general multi-layer (two layers in this case) extruder, which has been conventionally used for manufacturing various synthetic resin molded products having a multi-layer structure, is used. The thermoplastic fluororesin for the inner layer 2 and the carbon powder-thermoplastic fluororesin mixture for the outer layer 3 are melted respectively, and are concentrically formed by a two-layer tubular extrusion die so that the former is inside and the latter is outside. It suffices if they are merged and continuously extruded.

Here, as the thermoplastic fluororesin,
For example, copolymer resin of tetrafluoroethylene and perfluoroalkyl vinyl ether, ternary copolymer resin of tetrafluoroethylene, perfluoroalkyl vinyl ether and hexafluoropropylene, copolymer resin of tetrafluoroethylene and propylene hexafluoride. Particularly, a copolymer resin of tetrafluoroethylene and perfluoroalkyl vinyl ether is preferable in terms of moldability and heat resistance. Commercially available products of these thermoplastic fluororesins include Teflon PFA, Teflon EPE, manufactured by E. I. DuPont, USA
The same Teflon FEP is available.

As the carbon powder, any of various kinds of carbon black known as an antistatic compounding agent for synthetic resins can be used, and in particular, a fiber powder such as Ketjen black is preferable. ..

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

In order to obtain such a bellows-like outer shape, the tube 1 having a smooth peripheral surface as in the first embodiment may be softened by heating 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 secondary processing is indispensable in order 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 can be added to the inner layer 2 and the outer layer 3 if necessary.

[0023]

According to the present invention, as a chemical resistant tube made of a fluororesin, it has an excellent antistatic effect, a long product can be produced by continuous means, and the fluid passing through the tube extremely contaminates impurities. It can be used even when disliked, and can be provided at low cost, which can be applied to prevent static electricity on the outer surface side of pipes, shafts, etc. arranged inside a tower tank or tank.

[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 tube 2 inner layer 3 outer layer 4 tube

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI technical display location B32B 27/18 D 6122-4F // B29K 27:12 4F B29L 9:00 4F 22:00 4F

Claims (2)

[Claims] 1. An inner layer made of a thermoplastic fluororesin,
A chemical resistant tube comprising an outer layer in which carbon powder is mixed in the fluororesin. 2. The inside of the melt of the thermoplastic fluororesin,
A tube having inner and outer layers according to claim 1 is continuously manufactured by a two-layer tubular extrusion molding with a melt of a thermoplastic fluororesin mixed with carbon powder as an outer side. Manufacturing method.