DE19507110A1 - Two layer insulating plastic tube mfr., for use in e.g. heating systems - Google Patents

Abstract

Prodn. of heat insulating plastic tubes involves foaming of the outer insulating tube directly onto a plastic inner tube (5). The foamed outer tube simultaneously bonds to the inner tube (5) and forms a closed outer skin. Appts. comprises an extruder (7) for melt homogenisation with a blowing agent from a storage unit (8) and a crosshead die (9) for applying the expandable melt around the inner tube (5). A multipart tool (11) for moulding the foam comprises profiled elements moving synchronously with the inner tube (5) and mounted on endless belts (10). Pref. the OD of the outer tube is kept constant until the foaming action ceases and the constant outer dimensions guarantees repeatability and a constant thermal conductivity. Foaming occurs in the closed tool chamber whose inner wall is formed by the inner tube and the outlet end by the completely foamed plastic. Both inner tube (5) and the outer wall of the continuously moving mould (11) move synchronously, the inner tube (5) being taken either from a tube coil or direct from an extruder in an in-line process. In a process variation an outer plastic sheath can be extruded to form an enclosing chamber around the foaming material and is drawn against the forming faces of the tool elements (11) by vacuum. The outer and inner (5) tubes can be concentric or eccentric to each other and in the latter case the reduced thickness is at the top. The cross-section of the outer tube may be non-circular.

Description

The invention relates to a method and a direction for the production of a thermally insulated pipe according to the preamble of claim 1.

There are thermally insulated plastic pipes in the Be rich in sanitary and heating technology as well as the kitchen mix industry known during or during after installation, thermal insulation in the form of flexible polyethylene foam or elastomer foam Hoses from the roll or in short pieces the media pipes are pushed on. Should be added later insulated, you use slotted Hoses made from the same materials that you use pushes the cables that have already been laid. The same the lines are often also used with relatively hard, half-shelled or slotted insulation pipes Polyurethane foam or mineral fibers are thermally insulated.

This type of insulation during or as the conclusion of the Installation requires additional time and can due to the known, rough construction site conditions and possible installation errors in the form of Cold and sound bridges cause that after following trades, d. H. for screed layers buildings, refuses further work due to recognizable defects or concerns. This way time delays of the construction project and erhebli additional costs.  

There are also thermally insulated plastic pipes known in the same field of application, where the medium-carrying pipe into a larger diameter corrugated protective tube is drawn, which outside then thermal insulation in the same as before described way. The corrugated protective tube is required to measure the length of the medium res when the temperature rises. Such pipes are called hot water drinking water pipes or Ra diator connection lines usually directly on the raw concrete ceiling of a building and the late included screed included. Would media-carrying pipe without an external protective pipe directly on the raw concrete ceiling and thus in the screed so would be due to the thermal changes forces occurring at higher temperatures and Tension to cracks in the screed or hard floor top coverings, for example tiles. Also at this pipe-in-pipe installation is also one external insulation necessary. It is in the warmth protection regulation in its thickness depending on the Thermal conductivity of the insulation material and the outside diameter of the pipe required by law, al but only in the event that the insulation is directly on the medium-carrying pipe is applied. For the Pipe-in-pipe laying, on the other hand, must be the equivalent Thermal conductivity acc. To DIN 52613 agrees and with those in the Heat Protection Ordinance required values are compared. The validity The thermal insulation regulation just got rich time in heating and plumbing and generally tightened many requirements. To that extent comes the question of safe thermal insulation applicable rules of technology and according to the law in more importance.  

The disadvantageous consequence of this legal requirement is especially for pipe-in-pipe installation with external insulation a disproportionately large amount compared to the medium pipe enlarged outer diameter of the entire structure, which is a higher insulation compensation layer Bullet insulation is required or if the raw concrete floor not through insulation up to the top edge of the cable construction is balanced, a greater screed thickness required. In any case, the construction costs will be increased dramatically.

Another disadvantage is the belated, time-consuming manoeuvrable insulation of the pipe-in-pipe pipe system the construction site with its known weak points, like cold and sound bridges due to poor hand workmanship.

The utility models G 83 18 005.2 and G 83 20 278.1 describe a pipe string for the water and hot water installation, in which a tube made of foam art fabric in coextrusion with the production of a fle xiblen plastic corrugated pipe on the outer pipes brought and with its surface by toothing, Welding and / or gluing sticks. Disadvantageous is also the disproportionately large outside diameter of the pipeline when required by law insulation thickness.

To these disadvantages regarding the large outside Avoiding knives has already been in the past Tried to be factory pre-insulated with foam Manufacture pipes and the foam layer directly to apply to the medium pipe. Such an execution form is in utility model G 85 09 929.5 wrote. For example, an art was encased fabric tube made of higher density polyethylene online  its manufacture or from the finished large coil starting with an outer layer consisting of Low density polyethylene of approximately 0.918-0.924 g / cm³ and a chemical blowing agent, for example as azodicarbonamide, H₂NCO-N = N-CONH₂, with cer settlement temperatures of <160 ° C and nucleation medium for a fine-pored cell structure. Extruded was this mixture of the outer tube layer at Tem temperatures below the decomposition temperature, so that a homogeneous layer on the medium-carrying Forms inner tube. The manufactured in this way, two-layer tube was electron-irradiated networked. This had the advantage that, on the one hand the properties of the medium-carrying inner tube, long-term strength in particular has been improved and on the other hand during the subsequent heating of the twin layered tube above the melting point of the poly ethylene and the decomposition temperature of the propellant the outer layer when foaming the propellant gas formed did not collapse. The Ver wetting prevented melting and collapse of the tube and the foam cell walls.

The outer foam layer produced in this way Polyethylene has a closed-cell structure and at about three to four times the thickness of the previously, however, the outer layer extruded a density of still about 0.60 g / cm³ and thus one more comparatively high thermal conductivity, which is not is desired. Lower densities and thus a ge rings thermal conductivity, d. H. low insulation thicknesses at the same time meeting the requirements of heat protection ordinance can be used with the process of che mixing does not reach foaming.  

There are also plastic pipes with jackets physically foamed polyethylene for use known in the automotive industry, the show coat serves as vibration protection. The physical Foaming, with the former blowing agent from the group the chlorofluorocarbons, chlorinated hydrocarbons substances or hydrocarbons and for reasons of Environmental protection nowadays carbon dioxide or stick be used, makes it possible to make one melted low density polyethylene (PE-LD) with the help of nucleating agents and propellants gas a fine cell foam with very little To produce density of about 0.01-0.02 g / cm³, the itself due to its low thermal conductivity (Thermal conductivity group 040) excellent as Insulation material suitable for pipes. The foam can already in the manufacture of the plastic tube line can be applied to this outside. Plastic pipes manufactured in this way with outer PE foam insulation are particularly on the Dimensional accuracy of the foam thickness and the structure of the Covered outer foam surface, critical to judge. When the PE gas containing LD melt from the annular die gap of an am End of an extruder flanged crosshead, through which the plastic pipe to be coated passes, the foam volume is now under Atmospheric pressure expanding propellant strongly enlarged. Because a homogeneous distribution of the ge dissolved aggregate gas present in the Melt during the melting and conveying process is not secured in the extruder screw, it will foam-like extrudate partially different in thickness ex panded so that dimensional fluctuations and non-compliance of thickness tolerances are common. The outer layer PE foam insulation applied in this way  shows cells (pores) torn open by the propellant, d. H. a torn, rough surface.

The invention proceeds differently. Your basic idea is reproduced in claim 1. Other characteristics of the Er invention are the subject of the subclaims. Erfin According to the inner tube is already at the manufacturer position of the finished pipe with the thermal insulation and foam adhesive firmly adhering to the inner tube layering. Because this is the foam in statu nascendi, that is, when it is formed into one Tube is formed, this happens to form a closed outer skin, which the dimensional accuracy of the finished pipe and the homogeneity of the foam ge ensures.

This can be done in a device according to claims 17 to 23. Here, the plastic inner tube through a quill crosshead (sheathing head) an extruder for the preparation of a propellant gas reservoir gene preferably led to PE-LD melt and from the nozzle gap of the crosshead continuously emerging, propellant-containing melt in a hollow expands from the front nozzle / Thorn surface of the quill crosshead and on it connected, movably arranged half Shell or multiple shell shapes of two or more rerer continuously circulating mold chains as well which this room at the same speed as the plastic tube passing through the mold chains det. The molds can be made with a non-stick stratification, e.g. B. polytetrafluoroethylene (PTFE) verse hen and with air or preferably water or cold be medium chilled. The cooling causes the ex panding and the cavity filling PE foam  forms a closed outer skin, which according to claim 16 has a thickness of approx. 50 to 100 µm.

The limitation of the cavity described forward in the extrusion direction takes place by the cooling Foam. This ensures that the foam volume expands into a precisely limited cavity and become lighter in this due to the propellant gas Build up overpressure, on the one hand to the good port foam on the base tube and on the other to form a closed-cell, fine-pored PE foam with closed outer skin leads. The essentially happens with the characteristics of the new Method according to claim 2.

The foam casing produced in this way Rohres is ge in its external dimensions and structure according to claim 3 kept so even that physika properties such as heat conductivity of the network can be expected. It can be used for the post-insulated cables because of possible air gaps between pipe and Foam insulation or because of pipe-in-pipe systems the air gap between the medium pipe and the after Claim 8 and possibly also claims 9 and 10 provided corrugated protective tube on the one hand and protective tube and outer foam insulation of others the necessary complex measuring method with the heat pipe according to DIN 52613.

It has also been applied to the invention according to the foam-coated tube proved to be useful provided according to claim 12 concentric insulation to realize with the features of claim 13, with which the insulation is eccentrically placed on the pipe applies. The Thermal Protection Ordinance writes at  Thermal insulation of floor ceilings against below heated or unheated living rooms or against Outside air or soil-bound raw ceilings agreed insulation thicknesses depending on the thermal conductivity ability of the insulation used. this applies also for thermally insulated pipelines that directly on the floor ceiling will be laid. Delivered upwards Heat, similar to that of underfloor heating not taken into account, so that the top is thinner Insulation thicknesses can be selected. Combine for this use case the different insulation needs agility up and down, you get one eccentric foam arrangement with respect to the tube, the overall lower installation height of the thermal insulation floor ceiling.

Another advantage of the thermal insulation according to the invention ten Rohres is that compared to the conventional Pipe-in-pipe plumbing or heating pipes on the outer corrugated protective tube, which the longitudinal edges absorbs changes in temperature, waived can be. The soft PE foam enables through its flexibility the extent or the reserve pipe when temperature changes.

The details and further features of the invention result from the following description rerer embodiments of the invention directions based on the figures in the drawing. It demonstrate

Fig. 1 shows a schematic representation of a manufacturing plant for a thermally insulated plastic pipe,

Fig. 2 shows the essential part of the plant in Enlarge ter, more accurate representation,

Fig. 3 shows a modified form of the article of FIG. 1,

Fig. 4 shows a schematic representation of a further implementation form of Ferti shown in Fig. 1 generation plant,

Fig. 5 cross sections through various forms of execution of the subject invention.

In the manufacturing system shown in FIGS. 1 and 2 han it delt a so-called on-line manufacturing, in which the plastic pipe and the heat-insulating foam cladding is manufactured in a continuous system. Here, an extruder 1 with tube head 2 and calibration 3 , preferably vacuum tank calibration with subsequent cooling bath 4, first produces a plastic tube 5 , for example from polyolefinic materials such as polyethylene or polypropylene. This tube is fed via a trigger 6 to a second extruder 7 , the extremely long screw compared to conventional extruders a melt made of lower density polyethylene and which is then mixed with a gas supply station 8, the propellant gas for the subsequent foaming beige.

Instead of this extremely long extruder, two short, cascade-connected extruders are often used, with the first extruder serving for melt processing, the propellant gas being introduced between the two extruders via the adapter, and the second extruder merely for an intensive homogeneous distribution of the propellant gas in the melt and their continuous application via a foaming tool. According to the invention, the foaming tool is a so-called quill crosshead 9 , which is passed through by the extruded tube. On this cross head 9 two or more mold chains 10 with half-shell or multi-part molds 11 are connected sealingly at the same speed as the tube, so that an annular cylindrical cavity open towards the front in the extrusion direction, formed from the end face 12 of the quill cross head 9 one hand and the outer limits through the half-shell or multi-shell shapes 11 and the continuous plastic tube 5 on the other hand, ent. In this annular cavity, the propellant-containing melt 13 is continuously extruded through a nozzle annular gap 14 in the end face 12 of the quill crosshead 9 , where it expands and fills the cavity. Due to the speed of the continuous tube 5 and the circulating mold chain 10 , the continuity of the controlled foaming is ensured. The cooled molds 11 provided with a non-stick coating form the outer support of the expanding PE foam 15 . The foam filling process of the tube is followed by intensive cooling by means of water showers 16 , before it, depending on the diameter and flexibility, is either separated or sawed off into rods with suitable devices 17 , 18 or wound up as a bundle.

The system shown in Fig. 3 is used for off-line production. Here, an already finished plastic tube 5 , preferably made of electron beam or peroxidically cross-linked polyethylene, which additionally has an oxygen barrier coating made of ethylene vinyl alcohol (EVOH), is drawn off from a large coil 19 and coated with PE foam. In contrast to the on-line production according to FIGS. 1 and 2, the devices 1-4 fall away. The production system is identical to that of FIGS. 1 and 2, starting with trigger 6 .

In Fig. 4 a further manufacturing system is Darge, which differs from the system shown in Fig. 1, 2 and 3 only in that another extruder 20 is installed and the quill crosshead 21 now as a so-called double head or 2-layer Head formed and connected to both extruders 7 and 20 and that 11 vacuum can be applied to the circumferential half-shell molds, as is also practiced in corrugator machines for plastic corrugated tube production. The surfaces of the molds can be smooth or corrugated and contain small diameter holes to create a vacuum between the surface and the contacting plastic melt.

In otherwise the same manufacturing process as with the Anla conditions according to FIGS . 1, 2 and 3, a plastic tube 23 with a wall thickness of about 0.3-0.5 is additionally from the extruder 20 via the outer annular gap 22 of the 2-layer cross head 21 mm extruded and molded over the mold chain 10 applied to vacuum with molds 11 and calibrated to size. At the same time, the propellant-gas-containing, expandable PE foam 25 is extruded through the inner, second annular gap 24 of the 2-layer crosshead 21, which foams or fills the cavity between the outer thin tube 23 and the inner tube 5 . This creates an intimate bond between the outer tube 23 via the PE foam 25 to the inner tube 5 .

A further variant of a production plant according to Fig. 1, 2, 3 and 4, which is schematically not shown, is of the propellant-containing melt 13 aufbereitenden extruder 7 instead of a thermosetting for the preparation of foams, such example, polyurethane foam (PUR) dosing used installation with a mixing head for the two raw material components polyol and isocyanate. The mixing nozzle is then expediently mounted in the mandrel of the quill crosshead 9 , so that the foamable, reactive polyol / isocyanate mixture emerges from its end face 12 and, as previously described using the example of the systems according to FIGS. 1, 2, 3 and 4, the Fills the cavity.

In FIG. 5, embodiments of the invention are shown of thermally insulated plastic pipes. Fig. 5a shows in cross section the medium-carrying plastic tube 5 with an outer concentrically arranged PE foam coating 15 as thermal insulation. In Fig. 5b the same plastic pipe is shown with the same insulation thickness down, but an overall lower structure is achieved by the eccentric arrangement of the pipe. The same eccentric design is shown in Fig. 5c, wherein the thermal insulation 15 deviating from the circular shape can also be formed to other geometric shapes, for example as a rectangle.

In Fig. 5d as a further embodiment of the variant according to Fig. 5a, a thermally insulated plastic tube consisting of the inner tube 5 and the PE foam 15 is shown as thermal insulation with an outer, corrugated protective tube 23 in longitudinal section. The outer tube 23 serves as a protective tube for the pressure-sensitive, white Chen PE foam when using the thermally insulated plastic pipe in underground installation as a medium pipe for district heating lines or in rough construction site conditions.

To connect two thermally insulated plastic pipes according to the invention by welding or by means of clamping, pressing or sliding sleeve connectors, the thermal insulation 15 is separated from the inner plastic pipe 5 by means of a simple peeling device. Injection-molded parts with an adapted contour are used for the insulation of these connection points, so that there is a virtually seamless insulation.

Claims (25)

1. A process for the production of thermally insulated plastic pipes made of a plastic inner tube and an outer tube made of a foamable plastic, which is applied to the inner tube and thereby connected to it, characterized in that the foam in the outer tube of the foam in statu nascendi simultaneously with Connected to the inner tube and the outer tube is provided with an existing outer skin made of the foamed plastic. 2. The method according to claim 1, characterized in that that the diameter of the outer tube to the stand strength of the foam essentially constant is held. 3. The method according to any one of claims 1 or 2, because characterized in that the outside dimension of the outside tube and the structure of its foam like this be kept even that physical Sizes of the heat-insulating pipe, namely in the we considerably the thermal conductivity of the composite are calculable. 4. The method according to one or more of claims 1 to 3, characterized in that the Schaumbil until stability in a closed Molding space takes place, the inner wall of which is from the inside tube is formed. 5. The method according to one or more of claims 1 to 3, characterized in that when applying the foam onto a continuous inner tube  Outer wall of the mold space with essentially the same speed and the same direction as that Inner tube is moved. 6. The method according to one or more of claims 1 to 5, characterized in that the inner tube during ongoing production of the thermally insulated pipe is fed from a coil to the molding space. 7. The method according to one or more of claims 1 to 6, characterized in that the thermally insulated pipe in on-line manufacturing in the Molding space is extruded. 8. The method according to one or more of claims 1 to 7, characterized in that a cladding tube Forms the outer boundary of the mold space. 9. The method according to one or more of claims 1 to 8, characterized in that in on-line Fer the cladding tube to the inside of the molding space limit is extruded. 10. The method according to one or more of claims 1 to 9, characterized in that the cladding tube the inside of the mold space is curled. 11. The method according to one or more of claims 1 to 10, characterized in that the formation under one from the outside of the molding room Vacuum occurs. 12. The method according to one or more of claims 1 to 11, characterized in that the outer tube and the inner tube are arranged concentrically.   13. The method according to one or more of claims 1 to 11, characterized in that the external and the inner tube is arranged eccentrically, that the insulation with the lower thickness above lies. 14. The method according to one or more of claims 1 to 13, characterized in that the outer tube a cross-section deviating from the circular shape having. 15. The method according to one or more of claims 1 to 14, characterized in that for the inside pipe a thermoplastic or a thermoelastic shear plastic and a thermo for the outer tube more plastic, thermoelastic or thermoset Foam is used. 16. The method according to one or more of claims 1 to 15, characterized in that the outer skin closed cell and with a thickness of approx. 50- 100 microns is formed. 17. An apparatus for performing the method according to one or more of claims 1 to 16, characterized by an extruder ( 7 ) for processing a melt from the plastic of the thermal insulation and / or for distributing propellant gas for foam formation in the melt ( 13 ) with a foaming tool ( 9 ) for application to the inner tube ( 5 ) and a multi-part mold ( 11 ) as the outer boundary of the mold space, the forming parts of which are arranged on the interacting endless elements ( 10 ) which synchronously with the speed of the Umlau fen form ( 11 ) incoming inner tube ( 5 ). 18. The apparatus according to claim 17, characterized by a plurality of extruders, one of which is used to process the melt ( 13 ) and passes this to a further extruder, a propellant gas inlet being provided between the two extruders and the second extruder for uniform distribution of the propellant gas in the processed one Melt serves. 19. Device according to one of claims 17 or 18, characterized in that the extruder ( 7 ) serving for the discharge of the melt has a quill cross head ( 9 ) which delimits the insertion side of the molding space. 20. The device according to one or more of claims 17 to 19, characterized in that the umlau fenden molded parts ( 11 ) are provided with a non-stick coating. 21. The device according to one or more of the claims 17 to 20, characterized in that the shape parts with air, water or a refrigerant are cool. 22. The device according to one or more of claims 17 to 21, characterized in that the shaped parts ( 11 ) have openings for applying a vacuum. 23. The device according to one or more of claims 17 to 22, characterized in that a further extruder ( 20 ) is used for the coextrusion of the cladding tube and the quill crosshead ( 21 ) is designed as a two-layer double head and is connected to the extruder (s) ( 7 , 20 ) is connected. 24. The device according to one or more of the claims 17 to 23, characterized in that the Aufbe dosing of the melt containing propellant gas system with mixing head for polyol / isocyanate compo is used for thermal insulation. 25. The apparatus according to claim 24, characterized in that the mixing nozzle in the mandrel of the quill cross head ( 9 ) is mounted such that at its end face ( 12 ) polyol-isocyanate mixture emerges and fills the mold space.