NO764127L - - Google Patents

Description

Pipe or hose for transporting gases or liquids

especially under high pressures and temperatures.

The present invention relates to pipes or hoses for the transport of liquid or gaseous media, particularly at high temperatures and high pressures, where the hose wall is made up of several insulating layers.

For the transport of liquid or gaseous media under low pressure, a flexible pipeline is already known (German specification document 2125575), which consists of two coaxial pipes.

The interior of these coaxial tubes consists of a polyolefin and it

outer casing pipes of a polyamide, where the pipes are joined at each end by a joint during the formation of the pipelines. The inner tube, which should provide protection against chemical attacks from liquids or gases in the tube, can for example be made of polyethylene with a high specific gravity or of polytetrafluoroethylene, while the jacket tube, which serves as a protective covering and provides resistance to wear, shock and deformations when subjected to external stress, consists of polyamide . This construction is expressly intended for the transport of media under low pressure, as those with high temperatures and pressure can only be transported with difficulty since the polyethylene begins to melt at a certain temperature and deformations or breakdown of the polyethylene must be expected if higher pressures are used at the same time .

According to the invention, they have now set themselves that task

to provide a pipe or hose for the transport of gases or liquids in such a way that it can absorb pressure and temperature fluctuations without damage, while the part of the line that is in contact with the liquid or gas is chemically resistant.

The task is solved according to the invention by at least one layer of the pipe wall consisting of a moisture-hardening material on

basis of thermoplastics, elastomers or thermoplastic rubber.

The choice of moisture-curing material leads to a pipe that is distinguished by high chemical resistance and temperature resistance. The pipeline can be produced in desired lengths and cannot be permanently deformed by bending or buckling loads in operation.

Particular advantages are obtained by continuing the invention

when at least the inner tube surrounding the transport medium consists of a moisture-cured base material. In this case, it has proved particularly advantageous that the inner high-temperature-resistant polymer layer is surrounded by a stable outer jacket. A cover made of polycarbonate, polypropylene or polyamide is particularly suitable for this.

A further advantage of the invention is achieved by the fact that the inner high-temperature-resistant layer of hardened compound can easily A be welded together with the outer dimensionally stable material by suitable choice of compounds. The welding can be achieved in a simple way by the outer tube being extruded over the inner one by a twinning process, e.g. in a dual extrusion head. Since a hardening process of the inner layer, which would make it difficult to join or weld the two pipes together, only takes place at a later stage under the influence of moisture, in this way an intimate connection can be achieved between the two layers and a practically uniform material. By using suitable propellants, a thicker foamed layer of polypropylene or polyamide or the like can also be formed as an outer layer so that, in addition to the supporting effect, a better thermal insulation of the hose element is achieved.

As . base material for moisture-curable layers when building a pipeline, compounds can be used, which is known from the siloxane technique (DAS 1794 028, DOS 2 411 141) where the siloxanes or the siloxane compound are grafted onto the basic molecule of thermoplastic, elastomer or thermoplastic rubber. Production of such mixtures can take place in such a way that, in a preceding mixing process, the solution of siloxane curing chemicals can be introduced into the base material via diffusion using a mixing device with a high speed of rotation, or by the solution containing curing agent being immediately added during processing and/or or the forming process. However, for mixtures that contain larger amounts of filler, a previous mixing process can be used

as known from the rubber and plastics industry.

In contrast to such processes, grafting of suitable compounds can be omitted when, in a continuation of the invention, compounds are used which can be hardened by the addition of compounds containing the silicon hydride group<=>Si-H group at one or more places in the molecule. When carrying out the invention, the base materials such as polyethylene, ethylene propylene, thermoplastic rubber etc. can be added to tin or zinc oxides, e.g. in amounts of 0.5-2.0 parts per 100 parts basic material. These substances have the special effect that, through chemical reactions inside the injection-molded material, they form water, which can start curing immediately after extrusion. Fire-retardant substances can also be added to the base material, depending on the area of use, for example the polyethylene in a mixture can be replaced up to 100% with chlorinated polyethylene.

The temperature resistance of the relevant pipes or hoses can also be achieved by the relevant layers being made of moisture-curable elastomers. Suitable basic materials are e.g. The TPR types from the company Uniroyal, the TR types from the company Shell and others. You can also use other suitable elastomers such as EPDM, EPM, nitrile rubber, which is sold under the trade mark "Hypalon" from de Pont, which is chlorosulfonated polyethylene, etc. In the latter case, it is appropriate to add to the elastomer mixture suitable anhydrous fillers such as microglass beads, glass fibers or high-melting synthetic resins, asphalts or pitches, e.g. gilsonite asphalt, in a prior mixing process. Quantities of up to 100 parts and preferably up to 50 parts of microglass spheres or short-cut glass fibers have proven particularly beneficial here, while the quantities of added high-melting anhydrous synthetic resins, asphalt or the like total up to 200 parts,

and preferably up to 100 parts.

The inner or outer layers can consist of the same or different base materials, e.g. of moisture-curable EPDM.

It can sometimes also be an advantage, e.g. in connection with pressure hoses, to extrude two layers on top of each other and as an intermediate hose use a reinforcing metal, glass or textile fabric or lightweight pipe.• The choice of base elastomers or base thermoplastics for the layer that comes into contact with the liquid or gas being transported corrects primarily according to the hardened polymer's resistance to these media. If it e.g. in a pipe or a pressure hose where oil is to be transported, an oil-resistant inner layer is chosen, e.g. of moisture-curable nitrile rubber. In this case, the choice of outer layer is based on the desire to make the pipe's compressive strength as high as possible. This does not only apply to the mixture's own mechanical properties. It must

above all, a good jointing ability or weldability is also required between the oil-resistant layer and any reinforcement inserts of metal, glass or textile braiding.

In order to improve the adhesiveness between the reinforcement inserts and the two layers, common adhesive agents can be added, e.g. copolymers of ethylene with acrylic acid and acrylic acid esters for metals and silanes for glass cloth or braiding. Silanes are already found in moisture-curable mixtures (grafted on), so that the effect of the adhesive-mediating silanes for glass fiber braiding is further increased.

The aforementioned advantages, particularly when incorporating reinforcement inserts in pipes and hoses with several layers, are of course not only achieved with pressure hoses whose layers consist of moisture-curable elastomer mixtures, but also with the aforementioned flexible pressure pipes made of moisture-curable thermoplastics such as HD polyethylene dg/or polyamide.

It can also be an advantage when manufacturing pipes and

hoses according to the invention if an outgassing is carried out immediately

bare prior to the shaping of the moisture curable material. Excess silane or volatile peroxide cleavage products or trapped air can in this way be easily removed from the mass flow so that blister formations are avoided and products with a high surface smoothness are obtained.

The invention will be described in more detail in connection with an embodiment example which applies to a double-walled polymer pipe for a hot water pressure line.

The inner tube 1 consists of moisture-cured material, for example polyethylene and preferably HD polyethylene whose molecule is grafted with a silane compound. As outer tube 2 serves e.g. a polypropylene tube that acts as a dimensionally stable outer casing.

This fixed outer shell is little exposed to the temperatures

that prevails in the medium being transported ensures that the inner tube, as at the elevated temperatures of 110-140°C, is not expanded or destroyed by the prevailing operating pressure.

Instead of polypropylene, the layer 2 can also consist of polyamide, which in itself is sensitive to hydrolysis and is therefore not suitable as an inner layer in contact with such media.

In addition to the design example shown, one can naturally also choose to make the inner layer 1 of a suitable material such as polycarbonate, which is protected against chemical attack by means of a moisture-hardened outer skin.

The possibility of mixtures that can be used for the conduit shown in the figure can be seen from the following examples 1 and 2.

Example 1

(Mixture for moisture-cured inner tube)

Example 2

Polymer pipes have a particularly low heat transfer coefficient when the layers used consist of a particularly strongly foamed material. For this, e.g. hardened polyethylene or polyurethane. The heat transfer figures for VPE foam with specific gravity between 150 and 250 kg/m 3 are, for example, of 0.05 to 0.06 W/mk and for a semi-hard polyurethane foam with a volume weight between 50 and 100 kg/m 3 of 0.028 to 0.034 W/mk.

Depending on the desired heat loss, the maximum heat output can be set through the layer thickness. The following layer thickness will therefore be particularly energy-saving:

To make a heat-insulated pipe mechanically resistant to high stresses on the construction site, you need a jacket around the foam coating. This can e.g. consist of a solid polymer sheath which may consist of non-foamed polyethylene or may be applied

separately by the polyurethane foam insulation.

Claims (11)

1. • Pipe or hose for the transport of liquid or gaseous media, in particular at high temperatures and high pressures, whose wall is made up of several insulating layers, characterized in that at least one layer in the pipe wall consists of a moisture-hardening material based on thermoplastics, elastomers or thermoplastic rubber. 2. Pipe or hose according to claim 1, characterized in that at least the layer bordering the medium consists of a moisture-hardening material. 3. Pipe or hose according to claim 1 or 2, characterized in that the inner layer is surrounded by a mechanically resistant outer sleeve. 4. Pipe or hose according to claims 1-3, characterized in that the insulating layers are welded together. 5. Pipe or hose according to claims 1-4, characterized in that the base material for the moisture-hardening layer is compounds containing one or more silicon hydride groups -Si-H in the molecule. 6. Pipe or hose according to claims 1-5, characterized in that the base material contains tin or zinc oxide in an amount of 0.5-2 parts per 100 parts base material. 7. Pipe or hose, as stated in claims 1-6, characterized in that the base material has added fire-retardant substances such as chlorinated polyethylene in an amount of up to 100%. 8. Pipe or hose., as specified in one or more of claims 1-7, characterized in that metal wire, glass fiber or glass fiber fabric and/or textiles are inserted between the layers to increase the compressive strength. 9. Pipe or hose, as specified in claim 8, characterized in that the inserts are welded together or glued together with the upper and/or underlying layer. 10. Pipe or hose, as stated in claim 1 or later claims, characterized in that the moisture-curable base material contains up to 100 parts and preferably up to 50 parts of microglass beads or short-cut glass fibers as filler. 11. Pipe or hose, according to one or more of the above claims, characterized in that the moisture-curable base material preferably consists of elastomeric or thermoplastic rubbers to which fillers have been added in the form of high-melting anhydrous synthetic resins and/or pitch and/or natural asphalt up to a total of 200 parts and preferably up to 100 parts.