Thermally insulated medium pipes comprising hfo-containing cell gas

Abstract

The invention relates to a method for manufacturing a thermally insulated conduit (1) comprising at least one medium pipe (4), at least one thermal insulation layer (3) arranged around the medium pipe, and at least one outer jacket (2) arranged around the thermal insulation layer, wherein the outer jacket (2) optionally comprises a plastic barrier (9), and wherein the thermal insulation layer (3) comprises a foam whose cell gas contains at least 10 vol% HFOs, and wherein the thermal insulation layer (3) is formed by foaming a plastic composition which contains polymer components for foam formation and HFOs as a blowing agent. Such a conduit exhibits good insulation properties, a good environmental footprint, and is easy to manufacture.

Description

[0001] The invention relates to pipe systems containing thermal insulation, in particular thermally insulated carrier pipes and thermally insulated cover devices or sleeves for connecting line pipes with improved thermal insulation. Furthermore, the invention relates to methods for producing such devices and the use of polymer foams containing hydrofluoroolefins (HFO) in such devices and for producing such devices. Finally, the invention relates to the use of HFO as a cell gas in thermal insulation.

[0002] Pipe systems containing thermal insulation, also called pre-insulated pipe systems or thermally insulated pipe systems, are well-known and proven. Such pipe systems comprise flexible or rigid carrier pipes which are surrounded by thermal insulation, which in turn is surrounded by a casing, as well as, if necessary, sleeves and / or cover devices. Depending on their design, these pre-insulated pipe systems are referred to as plastic carrier pipe systems (PMR) or plastic casing pipe systems (KMR). In the former, the carrier pipes used have a certain degree of flexibility, so that the entire assembly can be wound onto drums with a certain amount of force. They are therefore also referred to as flexible pipe systems. In the latter, the carrier pipes used are not bendable, which is why the entire assembly is also referred to as rigid pipe systems. Accordingly, thermally insulated carrier pipes orPipes with one or more thermal insulation layers are known, as is their production. EP0897788 and EP2213440 disclose methods for the continuous production of thermally insulated medium pipes. EP2248648 discloses a method for the production of individual, rigid pipe sections.

[0003] In such piping systems, the composition of the cell gases in the foam (e.g., polyurethane, PU), which is typically used as insulation material, changes over time. This occurs through the diffusion of nitrogen and oxygen from the environment into the foam and through the diffusion of the foam or cell gases originally contained in the foam, particularly carbon dioxide and other blowing agents, out of the foam. The air gases have a significantly higher thermal conductivity than the carbon dioxide originally contained in the foam and the blowing agents commonly used.

[0004] In order to minimize these diffusion processes, it was proposed to integrate so-called barrier layers into the outer jacket.

[0005] Metallic layers can be used as barrier layers. The use of metallic layers not only completely prevents gas exchange, which is desirable, but also completely prevents water vapor from diffusing. This is particularly problematic when using plastic carrier pipes, as these typically carry water as the medium, which is why a small amount of water vapor constantly migrates through their walls. This water vapor must be able to escape to the outside or reach equilibrium with the environment, otherwise, over time, water will accumulate in the thermal insulation of the thermally insulated pipe, significantly increasing its thermal conductivity and posing the risk of permanent damage to the thermal insulation.

[0006] Layers consisting of one or more polymeric materials can be used as barrier layers. EP1355103, for example, describes thermally insulated pipes containing a barrier layer of ethylene vinyl alcohol (EVOH), polyamide (PA), or polyvinylidene dichloride (PVDC). Furthermore, EP2340929 describes a plastic-jacketed pipe whose outer jacket is designed as a multi-layer pipe and has a gas permeation barrier layer ("barrier") inside. The pipes described in these documents are difficult to manufacture and / or have insufficient insulation properties. CH710709 (post-published) and WO2004 / 003423 disclose pipes with thermal insulation and a polymeric barrier layer; these polymers contain polyketones or EVOH.

[0007] Fittings and connectors are used to connect thermally insulated pipes. In particular, cover shells, as described in WO2008 / 019791, are used as fittings. Alternatively, sleeves are used as connectors, especially when connecting rigid pipes. The aforementioned problems also arise with such fittings and connectors.

[0008] It is an object of the invention to provide a thermally insulated pipe as well as fittings and connecting pieces which do not have the aforementioned disadvantages.

[0009] The objects outlined above are achieved according to the independent claims. The dependent claims represent advantageous embodiments. Further advantageous embodiments can be found in the description and the figures. The general, preferred, and particularly preferred embodiments, areas, etc., given in connection with the present invention can be combined with one another as desired. Likewise, individual definitions, embodiments, etc., may be omitted or irrelevant.

[0010] The present invention is described in detail below. It is understood that the various embodiments, preferences, and ranges disclosed and described below can be combined with each other in any desired way. Furthermore, depending on the embodiment, certain definitions, preferences, and ranges may not apply. Furthermore, the term "comprising" includes the meanings "containing" and "consisting of."

[0011] The terms used in the present invention are used in the generally customary sense familiar to the person skilled in the art. Unless the direct context indicates otherwise, the following terms have in particular the meaning given here / Definitions.

[0012] The present invention is further characterized by the Figuresillustrated; in addition to the following description, further embodiments of the invention can be seen in these figures. Fig. 1 shows a schematic cross-sectional view of the structure of a conduit pipe (1) according to the invention. (2) The outer casing faces the environment with its outer side (6) and the inner side (5) facing the thermal insulation; (3) the thermal insulation is indicated with cell gas; (4) the carrier pipe. Fig. 2 schematically shows the structure of a preferred embodiment of the outer jacket (2). Here, (7) is the outer polymer layer (especially thermoplastic); (8) an outer adhesion promoter layer; (9) the barrier layer; (10) an inner adhesion promoter layer; and (11) the inner polymer layer (especially thermoplastic). Fig. 3shows a graphical representation of the dependence of the thermal conductivity value (abscissa in mW / m*K) of a PU foam measured at 50 °C on the composition of the cell gas (ordinate in vol%). The squares represent cyclopentane, the circles CO2, and the triangles HFO. Fig. 4 shows a graphical representation of the average pore size (abscissa in µm) of a PU foam as a function of the cell gas composition (ordinate in vol%). The squares represent cyclopentane, the circles CO 2 , and the triangles HFO. Fig. 5 shows a graphic representation of the viscosity (abscissa in mP*sec) of a polyol with various contents (ordinate in wt%) of cyclopentane or HFO 1233zd. The squares represent cyclopentane, the triangles HFO.

[0013] In a first aspect The invention thus relates to a pipe system containing thermal insulation (also called a pre-insulated pipe system or thermally insulated pipe system), in which said thermal insulation comprises a foam whose cell gas contains hydrofluoroolefins (HFOs). Such pipe systems, but without the said cell gas, are known per se and include thermally insulated pipes, sleeves, and cover devices for connecting such pipes.

[0014] In a first embodiment, the invention relates to a thermally insulated pipe (1), comprising at least one carrier pipe (4), at least one thermal insulation (3) arranged around the carrier pipe and at least one outer casing (2) arranged around the thermal insulation, characterized in that said outer casing (2) optionally comprises a barrier (9) made of plastic, and in that said thermal insulation (3) comprises a foam whose cell gas contains the components defined below.

[0015] In a second embodiment, the invention relates to a covering device made of plastic, in particular for the connection points of at least two pipe sections which are connected there, wherein the covering device has at least one thermal insulation (3) and at least one outer casing (2) arranged around the thermal insulation, characterized in that said outer casing (2) optionally comprises a barrier made of plastic, and in that said thermal insulation (3) comprises a foam whose cell gas contains the components defined below.

[0016] In a further embodiment, the invention relates to a sleevemade of plastic for the connection of thermally insulated pipes, wherein the sleeve comprises at least one thermal insulation (3) and at least one outer casing (2) arranged around the thermal insulation, characterized in that said outer casing (2) optionally comprises a barrier made of plastic, and in that said thermal insulation (3) comprises a foam whose cell gas contains the components defined below.

[0017] This aspect of the invention will be explained in more detail below

[0018] Thermal insulation (3): The thermal insulation partially or completely encloses the carrier pipe, preferably completely. Foamed plastics ("foams"), which contain a cellular gas within their cells, are particularly suitable for thermal insulation. The thermal insulation can be homogeneous along its cross-section or composed of several layers. Typically, the thermal insulation in pipes is homogeneous.

[0019] Cell gases: Cell gases are the gases present in thermal insulation. These are a result of the manufacturing process and consist of chemical and physical blowing agents, or their reaction products. Typically, such cell gases are added during the foaming process or are formed during it.

[0020] According to the present invention, the cell gas in the thermal insulation foam is characterized by containing hydrofluoroolefins (HFOs). The cell gas can consist of only one or more HFOs and may optionally contain additional components. Advantageously, the cell gas contains 10-100 vol% HFOs, preferably 20-100 vol% HFOs, more preferably 30-100 vol% HFOs, particularly preferably 40-100 vol% HFOs, and most preferably 50-100 vol% HFOs. Accordingly, the cell gas can contain additional components.

[0021] In one embodiment, the cell gas contains 0-50 vol% (cyclo)alkanes, preferably 0-45 vol% (cyclo)alkanes, more preferably 0-40 vol% (cyclo)alkanes, particularly preferably 0-35 vol% (cyclo)alkanes. The ratio of HFOs to (cyclo)alkanes is preferably at least 2.5:1, preferably at least 3:1.

[0022] In a further embodiment, the cell gas additionally or alternatively contains up to 50 vol% CO2, preferably 0-40 vol% CO2, particularly preferably 0-30% CO2.

[0023] In a further embodiment, the cell gas additionally or alternatively contains up to 5 vol% nitrogen (N 2 ) and / or oxygen (O 2 ).

[0024] These additional components can be added to the blowing agent, such as the (cyclo)alkanes mentioned above; they can be formed during foam production, such as CO 2 ; they can enter the foam during the production process, such as air, O 2 , N 2 .

[0025] It has been surprisingly shown that even at such low levels as 10 vol% HFO in the cell gas, the properties of pipe systems, especially thermally insulated pipes, are improved in a number of respects.

[0026] Specifically, it was found that the pipes described here exhibit surprisingly improved insulation performance. Without wishing to be bound by any theory, it is assumed that the improved insulation properties are due not only to the material properties of the HFOs (thermal conductivity), but also to improved foaming caused by the changed viscosity.

[0027] In the case of PU foams and PIR foams, the addition of HFO to one of the two starting components (isocyanate or polyol) or during direct mixing in the mixing head leads to a significant reduction in viscosity. Without wishing to be bound by any theory, it is assumed that the reduced viscosity improves the mixing of the two components and thus promotes the formation of comparatively smaller cells.

[0028] To achieve a similar reduction in viscosity with cyclopentane as a blowing agent, its concentration could alternatively be increased by, for example, 1.86 times. This would be the factor by which the molecular weights of HFO 1233zd (130.5 g / mol) and cyclopentane (70.2 g / mol) differ, but this would have several adverse consequences: a) Firstly, twice the amount of propellant gas would expand during the foaming process, leading to uncontrollable changes in the foam structure. Existing PU foams and production facilities are optimized for the smaller amount of cyclopentane, and significant changes in the quantity of expanding blowing agent would require extensive new developments. b) Cyclopentane acts as a plasticizer for the PU foam. A 1.86-fold increase in the amount leads to its significant softening. This is undesirable, on the one hand, because the foam plays a supporting role, i.e., it is essential for the mechanical stability of the entire composite. On the other hand, this is undesirable because the increasing softness of the foam during the manufacturing process causes the entire pipe composite to deviate more and more from the ideal round cross-sectional geometry.Thus, it has been found that the complete or partial replacement of cyclopentane with HFOs improves the mechanical properties of the foam. Cyclopentane is typically added to the starting material to reduce its viscosity; however, the maximum amount is limited by the requirement for the resulting foam to have sufficient mechanical strength. By replacing cyclopentane with HFOs, these conflicting goals can be achieved. The use of a comparable amount of HFO results in starting materials with lower viscosity while maintaining the same mechanical strength of the final foam. Thus, manufacturability can be improved while maintaining product quality.

[0029] Furthermore, it was found that adding HFO to one of the starting components, or directly adding it to both starting components in the mixing head, reduces their flammability. This effect is very beneficial because it reduces the safety requirements for such a production plant, significantly simplifies the design of such a production plant, and thus saves costs that would otherwise be incurred when working with flammable propellants.

[0030] In summary, it can be stated that the known problems can be solved elegantly by partially or completely replacing cyclopentane (Cp) with HFOs. On the one hand, more blowing agent can be added, leading to the desired viscosity reduction. At the same time, the expanding effect remains essentially unchanged, and no fundamental adjustments to the formulation and production plant are required. Ultimately, replacing the flammable cyclopentane with the non-flammable HFO improves occupational safety and reduces the investment costs for such a production plant.

[0031] It has also been found that high levels of (cyclo)alkanes, especially cyclopentane, have a negative impact on product quality. Experience has shown that excessive cyclopentane content in the polyol leads to the formation of large bubbles in the foam, which are caused by the blowing agent (especially cyclopentane) being expelled from the foam by the temperature of the forming PU foam.

[0032] In a continuous production process, the outer jacket is usually applied by extrusion and, due to the high temperature of typically 80–250°C, is in a state at this time where it is easily deformed. The bubbles then become visible on the outside of the insulated pipe because the escaping blowing agent inflates the outer jacket. This applies equally to insulated pipes with a corrugated, smooth, and corrugated outer jacket. The escape of the blowing agent is promoted by the temperature of the extruded outer jacket. Pipes with such defects are considered scrap and can no longer be used for their intended purpose.

[0033] The formation of bubbles is prevented if the content of cyclopentane in the cell gas composition of the resulting insulating foam is 0-50 vol%, preferably 0-45 vol%, particularly preferably 0-40 vol%, most preferably 0-35 vol%.

[0034] Surprisingly, it was found that the aforementioned blistering does not occur when HFO is used as a blowing agent. This is especially true when the HFO content in the cell gas composition of the resulting insulating foam is within the aforementioned limits. The described behavior is all the more surprising given that the boiling points of HFO 1233zd and HFO 1336mzz are 19 °C and 33 °C, respectively. This compares to cyclopentane, whose boiling point is 49 °C. Based on these boiling points, it is expected that blistering would be more pronounced when using low-boiling HFO as a blowing agent than when using higher-boiling (cyclo)alkanes, e.g., Cp. The opposite was observed.

[0035] Hydroolefins(HFOs) are known and commercially available or can be produced using known methods. These are suitable as propellants, particularly because of their low global warming potential (GWP) and their harmlessness to the ozone layer of the atmosphere (ozone depleting potential, ODP). The term includes both compounds that contain only carbon, hydrogen, and fluorine, as well as compounds that also contain chlorine (also known as HFCO) and each contain at least one unsaturated bond in the molecule. HFOs can exist as a mixture of different components or as a pure component. HFOs can also exist as isomeric mixtures, particularly E / Z isomers, or as isomerically pure compounds.

[0036] Particularly suitable HFOs in the context of the present invention are selected from the group comprising compounds of the formula (I) wherein R 5< stands for H, F, Cl, CF 3 , preferably Cl, CF 3 , and R 6< stands for H, F, Cl, CF 3 , preferably H.

[0037] Particularly suitable HFOs are R1233zd (e.g. Solstice LBA, Honeywell) and R1336mzz (e.g. Formacel 1100, Du-Pont).

[0038] It has surprisingly been found that the pipes described here exhibit improved insulating properties when the cell gases of the insulation contain at least 10 vol%, preferably at least 30 vol%, particularly preferably at least 50 vol% HFO. It has also been shown that the addition of such HFOs to the starting materials of the foam insulation leads to improved manufacturability.

[0039] (Cyclo)alkanesare known as cell gas for insulation in thermally insulated pipes. The alkane or cycloalkane in question is advantageously selected from the group comprising propane, butane, pentanes, cyclopentane, hexanes, and cyclohexane. By combining (cyclo)alkane with HFO, product properties can be fine-tuned, and / or manufacturability can be improved and / or costs can be reduced with acceptable quality losses. The (cyclo)alkanes mentioned can exist as pure compounds or as mixtures; the aliphatic alkanes can exist as isomerically pure compounds or as isomer mixtures. A particularly suitable (cyclo)alkane is cyclopentane.

[0040] Carbon dioxide:If the foam is made from PU or polyisocyanurate (PIR), a certain amount of CO2 is typically produced, as the starting material, technical-grade polyol, normally contains a small amount of water. This then reacts with the isocyanate to form carbamic acid, which spontaneously releases CO2. The CO2 content of the cell gas is therefore linked to the purity of the starting materials and is typically below 50 vol.%. If the starting materials are anhydrous, e.g., when foaming polyolefins, the CO2 content of the cell gas is 0 vol.%. The CO2 content of the cell gas can therefore be influenced by the choice of starting materials (or their purity).

[0041] Other cell gases:During production, components from the atmosphere / ambient air can enter the cell gas. These are primarily N2 and / or O2, e.g., air. The content of these cell gases is typically below 5 vol.%. If the production facility is specially designed, contact with the atmosphere / ambient air can be avoided, and the content of other cell gases is kept at 0 vol.%.

[0042] Foam:Said thermal insulation (3) comprises (i.e., contains or consists of) a foam. Such foams are known per se; particularly suitable are foams that comply with the standards DIN EN 253:2015-12 (particularly for CMR) and EN15632-1:2009 / A1:2014, EN15632-2:2010 / A1:2014, and EN15632-3:2010 / A1:2014 (particularly for PMR). The term encompasses rigid foams and flexible foams. Foams can be closed-cell or open-cell, preferably closed-cell, in particular as set out in the standard DIN EN 253:2015-12. Such foams are preferably selected from the group of polyurethanes (PU), polyisocyanurates (PIR), thermoplastic polyesters (particularly PET), and thermoplastic polyolefins (particularly PE and PP).

[0043] The following combinations of foam and cell gas have been shown to be particularly advantageous: PU containing 50-100 vol% R1233zd and 0-50 vol% Cp; PU containing 50-100 vol% R1336mzz and 0-50 vol% Cp; PIR containing 50-100 vol% R1233zd and 0-50 vol% Cp; PIR containing 50-100 vol% R1336mzz and 0-50 vol% Cp; PET containing 50-100 vol% R1233zd and 0-50 vol% Cp; PET containing 50-100 vol% R1336mzz and 0-50 vol% Cp; PE containing 50-100 vol% R1233zd and 0-50 vol% Cp; PE containing 50-100 vol% R1336mzz and 0-50 vol% Cp.

[0044] In one embodiment, the aforementioned cell gases complement each other to 100 vol%. In another embodiment, these cell glasses, together with CO2 and air, complement each other to 100%. In another embodiment, the HFO:Cp ratio is at least 2.5:1.

[0045] It has also been shown that the following combinations of foam and cell gas are particularly advantageous: PU containing 50-100 vol% R1233zd and 0-50 vol% Cp and 0-50 vol% CO 2 ; PU containing 50-100 vol% R1336mzz and 0-50 vol% Cp and 0-50 vol% CO 2 ; PIR containing 50-100 vol% R1233zd and 0-50 vol% Cp and 0-50 vol% CO 2 ; PIR containing 50-100 vol% R1336mzz and 0-50 vol% Cp and 0-50 vol% CO 2 PU containing 50-100 vol% R1233zd and 0-45 vol% Cp and 10-40 vol% CO 2 ; PU containing 50-100vol% R1336mzz and 0-45 vol% Cp and 10-40 vol% CO 2 ; PIR containing 50-100vol% R1233zd and 0-45 vol% Cp and 10-40 vol% CO 2 ; PIR containing 50-100vol% R1336mzz and 0-45 vol% Cp and 10-40 vol% CO 2 .

[0046] In one embodiment, the aforementioned cell gases complement each other to 100 vol%. In another embodiment, these cell gases, together with air, complement each other to 100%. In another embodiment, the HFO:Cp ratio is at least 3:1.

[0047] In a further embodiment, the thermal insulation consists of the aforementioned foams and the aforementioned cell gases.

[0048] Barrier (9) Diffusion barriers are known per se in the field of conduits / pipe systems. If a barrier is present, this barrier is formed as a layer. It is preferred that at least one barrier (9) is present as described below. It is particularly preferred that a barrier (9) is present as described below. This layer (9) enables the diffusion of cell gases out of the thermal insulation and of gases outside the conduit (especially air) into the thermal insulation to be reduced. This property is important to ensure the insulating capacity of the conduit / pipe system over a longer period of time.

[0049] In an advantageous embodiment, this layer also allows water to diffuse out of the thermal insulation. This property is particularly important for pipes / pipe systems whose carrier pipe (4) is made of plastic. If an aqueous medium is transported in such pipes / pipe systems, water from the medium can penetrate the insulation through the pipe, thus reducing its insulating capacity and damaging the insulation material.

[0050] In an advantageous embodiment, this layer also allows for a certain permeability for CO 2. A particularly suitable value for the CO 2 permeability is in the range of 0.5 - 100 cm 3 < / m 2 < *day*bar. A barrier with selective properties is therefore advantageous, in particular: (i) permeable to water and water vapor, (ii) impermeable to the cell gases which have a low thermal conductivity, (iii) permeable to the cell gases which arise during production but have a relatively high intrinsic thermal conductivity (e.g. CO 2 ), (iv) impermeable to the gases from the environment, in particular nitrogen, oxygen and air.

[0051] It has been shown that a conduit of the type mentioned above, in which the barrier comprises one or more of the polymers listed below, meets the requirements very well. According to the invention, the barrier can be present in a single layer or in several separate layers. Furthermore, the barrier can be attached to the insulation or the outer casing or in the outer casing by means of an additional layer ("adhesion promoter layer" (8), (10)).

[0052] The barrier (9) can be arranged as a layer in the outer casing (2); this is preferred, in particular this embodiment is preferred with two adhesion promoter layers (8, 10) adjacent to the barrier (9) as in Fig. 2 explained.

[0053] Furthermore, the barrier can be arranged as a layer on the outside and / or inside of the outer shell. Furthermore, the barrier can be formed by the outer shell. Furthermore, the barrier (9) can be arranged as a layer between the thermal insulation (3) and the outer shell (2). In this embodiment, the adhesion promoter layer is typically omitted.

[0054] The barrier layer (9) advantageously has a layer thickness of 0.05 - 0.5 mm, preferably 0.1 - 0.3 mm. If the barrier forms the outer shell, the barrier advantageously has a layer thickness of 0.5 - 5 mm. If present, the adhesion promoter layers (8, 10) advantageously have a layer thickness of 0.02 - 0.2 mm, independently of one another.

[0055] Preferably, the barrier comprises a copolymer of ethylene with carbon monoxide or with vinyl alcohol.

[0056] In an advantageous embodiment, the barrier comprises a polymer that contains or consists of polyketones. Accordingly, the polymer layer comprises polyketones and blends of polyketones, as well as laminates containing polyketones. Polyketones are known materials and are characterized by the keto group (C=O) in the polymer chain. In this embodiment, the polymer advantageously comprises 50-100 wt.%, preferably 80-100 wt.%, of structural units of formula (II) or formula (III). wherein o stands for 1 or 2, preferably 1, p stands for 1 or 2, preferably 1, q stands for 1-20 and r stands for 1-20.

[0057] Polyketones are obtained by the catalytic reaction of carbon monoxide with the corresponding alkenes, such as propene and / or ethene. Such ketones are also referred to as aliphatic ketones. These polymers are commercially available, for example, as polyketone copolymer (Formula II) or polyketone terpolymer (Formula III) from Hyosung. Such polyketones are also commercially available under the trade name Akrotek ®< PK. Suitable polymers have a melting temperature of over 200°C (measured with DSC 10 K / min according to ISO 11357-1 / 3) and / or possess a low water absorption of less than 3%, measured according to DIN EN ISO 62 (saturation in water at 23°C).

[0058] In an advantageous embodiment, the barrier comprises a polymer which contains ethyl vinyl alcohol or consists of ethyl vinyl alcohol.

[0059] In this embodiment, the polymer comprises 50-100 wt.%, preferably 80-100 wt.%, of structural units of formula (IV). wherein m stands for 1-10, n stands for 2-20.

[0060] Suitable ethyl vinyl alcohols are, in particular, statistical copolymers with a m / n ratio of 30 / 100 to 50 / 100. These polymers are commercially available, for example, as the EVAL FP series or EP series from Kuraray. They are characterized by good processability, particularly when coextruded with the normally used sheath material, polyethylene (PE), because their melt viscosities and melting temperatures are in a similar range.

[0061] The combination of cell gases from the hydroolefin group and barrier layers according to the formulas (II), (III), (IV) described here leads to particularly good, superadditive insulation properties of the thermally insulated pipes. Such a positive interaction of these components is surprising. Without wishing to be bound by any theory, this superadditive effect can be attributed to the barrier properties of the materials according to formulas (II), (III), (IV).

[0062] medium pipe (4): In principle, all carrier pipes suitable for thermally insulated pipes can be used. Accordingly, the carrier pipe can be a corrugated pipe, a smooth pipe, or a pipe with a corrugated casing; it can be a rigid and straight pipe section, a rigid bent pipe section, or a flexible pipe section.

[0063] The carrier pipe can be made of polymeric or metallic materials, preferably polymeric materials. Such materials are known per se and are commercially available or manufactured using known processes. The materials are selected by a person skilled in the art based on the intended use, if necessary, following routine testing.

[0064] In one embodiment, said medium pipe (4) is a flexible plastic pipe, the plastic being selected from the group acrylonitrile butadiene styrene (ABS), cross-linked polyethylene (PEXa, PEXb, PEXc), PE, polybutene (PB), polyethylene raised temperature (PE-RT), and polyketone (PK).

[0065] In a further embodiment, said carrier pipe (4) is a flexible plastic pipe with an outer metal layer, the plastic being selected from the group consisting of ABS, PEXa, PEXb, PEXc, PE, PB, PE-RT, and PK, and the metal being selected from the group consisting of aluminum, including its alloys. Such inner pipes are also known as composite pipes.

[0066] In a further embodiment, said medium pipe (4) is a rigid plastic pipe, the plastic being selected from the group ABS, PEXa, PEXb, PEXc, PE, PB, PE-RT and PK.

[0067] In a further embodiment, said medium pipe (4) is a flexible metal pipe, the metal being selected from the group consisting of copper including its alloys, iron including its alloys (such as stainless steels), and aluminum including its alloys.

[0068] In a further embodiment, said medium pipe (4) is a rigid metal pipe, the metal being selected from the group consisting of copper including its alloys, iron including its alloys (such as stainless steels), and aluminum including its alloys.

[0069] In a further embodiment of the carrier pipe (4), the aforementioned plastic barrier can be arranged on the outside of the inner pipe or it can be formed by the carrier pipe itself. A barrier on the carrier pipe, or formed by the carrier pipe itself, reduces the diffusion of vapor from the carrier pipe into the thermal insulation. According to the invention, such a ("second") barrier is combined with another ("first") barrier above the thermal insulation.

[0070] Outer jacket(2): In principle, any outer casing suitable for thermally insulated pipes can be used. Accordingly, the outer casing can be a corrugated pipe, a smooth pipe, or one with a corrugated casing. It can be a rigid and straight pipe, a rigid bent pipe, or a flexible pipe.

[0071] The outer jacket can be made of polymeric or metallic materials, preferably polymeric materials. Such materials are known per se and are commercially available or manufactured using known processes. The materials are selected by a person skilled in the art according to the intended use, if necessary after routine testing. Thermoplastic polymers, such as commercial PE types, are advantageously used. High-density PE (HDPE), low-density PE (LDPE), and linear low-density PE (LLDPE) are suitable. The layer thickness of the outer jacket (2) can vary widely but is typically between 0.5 and 20 mm, including any barrier and barrier layers.

[0072] In one embodiment of the invention, the outer shell contains the barrier described here, as described above. This embodiment is advantageous because the shell and barrier can be produced simultaneously and thus cost-effectively by coextrusion.

[0073] In an alternative embodiment of the invention, the outer jacket does not contain the barrier described here, as described above. In this embodiment, the barrier is present as a separate layer. This embodiment is advantageous because the jacket and barrier can be constructed separately and thus flexibly.

[0074] In an advantageous embodiment, the invention relates to a conduit pipe as described here, in which said outer casing (2) is designed as a corrugated pipe; and said carrier pipe is designed as a flexible pipe section and in particular has at least one carrier pipe based on polyethylene and a thermal insulation based on PU and an outer casing based on polyethylene.

[0075] In one further advantageous embodimentThe invention relates to a conduit as described here, in which said conduit is a rigid straight pipe section and in particular at least one carrier pipe based on polyethylene or steel and a thermal insulation based on PU and an outer jacket based on polyethylene.

[0076] In one further advantageous embodimentThe invention relates to a conduit pipe as described here, in which said outer casing (2) is designed as a corrugated pipe. Such conduit pipes are advantageously combined with a carrier pipe, which is designed as a flexible pipe section and in particular comprises at least one carrier pipe based on polyethylene or cross-linked polyethylene. Advantageously, such conduit pipes are further provided with thermal insulation (3) comprising a foam whose cell gas has the aforementioned composition (wherein the cell gas particularly preferably contains a maximum of 35% (cyclo)alkanes).

[0077] In a second aspect The invention relates to methods for producing thermally insulated pipes, sleeves, and cover devices as described here. Accordingly, the invention is based on the object of creating improved methods for producing a pipe, sleeve, or cover device that can be operated both continuously and discontinuously.

[0078] This aspect of the invention will be explained in more detail below.

[0079] In principle, the thermally insulated devices described here (cf. first aspect of the invention) can be manufactured analogously to known processes. The known blowing agents (e.g., cyclopentane, CO2) are partially or completely replaced by the HFOs described here. Accordingly, conventional systems can be used for production, if necessary after adaptation to new parameters, as can be carried out by a person skilled in the art in their routine work. The processes described in the documents EP0897788 and EP2213440 and EP2248648 and WO2008 / 019791 and EP1355103 and EP2340929 cited above are hereby incorporated by reference.

[0080] In an advantageous embodiment of the process, the thermal insulation (3) is formed by foaming a plastic composition containing polymer components for foam formation and HFO as a blowing agent. According to the invention, the HFO can either be metered into one of the components and then processed, or the starting components and the HFO can be combined simultaneously in a metering device (e.g., the mixing head).

[0081] In a further advantageous embodiment of the process, the plastic composition comprises two liquid components, the first component containing a polyol and HFO, and the second component containing isocyanate. The isocyanate component is preferably based on methylene diisocyanate. However, other isocyanates, such as those based on toluene-2,4-diisocyanate or aliphatic isocyanates, can also be used.

[0082] In a further advantageous embodiment of the process, the plastic composition comprises two liquid components, the first component containing a polyol and the second component containing isocyanate and HFO. HFO components that exhibit good miscibility with the two liquid components and whose boiling point is not too low (in particular, not below 10 °C) are particularly preferred. This minimizes the equipment required for production; cooling systems are required only to a limited extent.

[0083] In a further advantageous embodiment of the process, the plastic composition consists of a molten component and this melt is combined with HFO under pressure.

[0084] Variant 1:If the thermally insulated pipe of this invention comprises one or more flexible medium pipe(s) and the outer jacket (13) comprises a barrier made of plastic, a method variant is advantageous in which (a) the at least one carrier pipe is continuously fed and covered with a plastic film formed into a hose, (b) a foamable plastic composition is introduced into the space between the carrier pipe and the hose as a thermal insulation layer, (c) the carrier pipe and the hose are introduced into a tool formed from rotating molded parts and leave this tool at its end, and then (d) the outer jacket is extruded onto the surface of the hose, wherein the foamable plastic composition contains the polymer component(s) for foam formation and HFO as blowing agent. In this process variant, the barrier is introduced between the foamed thermal insulation layer and the inside of the outer jacket by forming the tube from the polymer; or the barrier is applied by coextrusion together with the outer jacket; or the barrier is applied directly to the tube; or a layer of the outer jacket is applied first, followed by the barrier and followed by at least a second layer of the outer jacket.

[0085] In this process variant, in step a, the inner tube be continuously drawn from a supply; or be continuously produced by extrusion.

[0086] Variant 2: If the thermally insulated pipe of this invention comprises one or more rigid medium pipe(s) and the outer jacket (2) with barrier made of plastic, a process variant is advantageous in which (a) a carrier pipe is centered within an outer casing, and (b) a foamable plastic composition is introduced into the space between the carrier pipe and the outer pipe as a thermal insulation layer, characterized in that the foamable plastic composition contains the polymer components for foam formation and HFO as a blowing agent. As already mentioned, said HFO can be mixed with the two liquid components in a mixing head, or said HFO is pre-mixed with one of the two components and then fed to a mixing head. In this process variant, the barrier between the foamed thermal insulation layer and the outside of the outer casing can be introduced in the form of a hose; or the barrier can be applied to the inside of the outer pipe; or the barrier can be provided in the outer pipe; or the barrier can be applied to the outside of the outer pipe.

[0087] Variant 3:If the thermally insulated pipe of this invention contains thermal insulation made of a thermoplastic foam, for example, PET, PE, or PP, a process variant is advantageous in which the HFO is injected directly into the molten polymer matrix, subsequently expanding to cause the thermoplastic to expand. This can be achieved, for example, by melting a polymer mixture in the extruder and feeding HFO into this melt under pressure. Upon exiting the mold, the blowing agent present causes foaming.

[0088] In a third aspect The invention relates to new uses of HFOs.

[0089] This aspect of the invention will be explained in more detail below.

[0090] In a first embodiment, the invention relates to the use of hydrofluoroolefins as cell gas for foam insulation in thermally insulated pipe systems, in particular in plastic medium pipe systems (PMR) and in plastic jacketed pipe systems (KMR).

[0091] HFOs can advantageously be used as cell gas in foam insulation of line pipes, cover devices and sleeves, in particular of line pipes, cover devices and sleeves as described here (first aspect).

[0092] The invention is described in the following Examples explained in more detail; these are not intended to limit the invention in any way. Example 1: Production of a conduit pipe according to the invention

[0093] Carrier pipes made of PExa with an outer diameter of 63 mm and a wall thickness of 5.8 mm were continuously unwound from a supply drum. Shortly before the foaming station, this carrier pipe was enclosed in a PE film, which in turn was unwound from a supply and fed via a forming shoulder. The appropriate amount of a mixture of a polymeric isocyanate based on diphenylmethylene diisocyanate (MDI) with an NCO content of 31% and a polyol with an OH number of 410 mg KOH / g (determined according to ASTMD4274D) and a water content of 0.8% was added to the tubular film, which was still open at the top. The isocyanate component was used slightly overstoichiometrically relative to the reactive OH groups. The two components were thoroughly mixed in a high-pressure mixing head at a pressure of 150 bar before addition.The appropriate amount of HFO / cyclopentane was first stirred into the polyol component. Immediately after adding the two-component mixture, the tubular film was sealed at the top. The resulting PU foam was forced into a cylindrical shape by molding, and after curing, a PE sheath was continuously extruded onto it.

[0094] The resulting tubes were analyzed for the cell gases contained in the foam. For this purpose, small samples of approximately 3 cm³ in size were punched out of the foam and mechanically destroyed in a closed system, allowing the cell gases to enter the measuring apparatus. The gases present were determined qualitatively and quantitatively using a gas chromatograph.

[0095] In addition, the thermal conductivity at 50 °C was measured on 3 m long pipe sections according to the standards DIN EN 253:2015-12 and EN ISO 8497:1996 (λ 50 value). Furthermore, the composition of the cell gas was determined (according to the Chalmers method; described in Rämnas et al., J. Cellular Plastics, 31, 375-388, 1995); this method was also used in the following examples. The summary of the results can be found in the following table, and a graphical representation is shown in Figure 3 visible: Cell gas Unit No.1.1 No.1.2 No.1.3 No.1.4 No.1.5 CO2 * [Vol%] 100 51 34 31 32 CP [Vol%] 0 46 14 9 0 HFO 1233zd [Vol%] 0 0 49 59 65 O2 + N2 [Vol%] 0 3 3 1 3 λ 50 value [mW / m*K] 25.8 23.1 21.7 20.2 19.6 * CO2 is inevitably formed as a by-product from the starting components and is not added (chemical blowing agent).

[0096] The data clearly demonstrate the positive influence of HFO on thermal conductivity. Example 2: Model test for foamable mixtures

[0097] A quantity of 380–420 g of polyol was placed in a beaker, and the amount of blowing agent specified in the table was stirred in. The viscosity of the solution was determined using a Brookfield Viscometer DV I-Prime rotational viscometer. The average value of three measurements was recorded.

[0098] The results are summarized in the table and in Fig. 5 shown graphically. Propellant Content of added propellant temperature viscosity [mol / 100 g polyol] [K] [mPa*s] Polyol Pure polyol, without blowing agent 292.8 2005 CP 0.043 293.2 1245 0.071 293.1 946 HFO 1233zd 0.041 293.0 1151 0.071 293.1 815

[0099] The data clearly demonstrate the positive influence of HFO on viscosity. Example 3: Pore size in PU foams

[0100] According to DIN EN 253:2015-12, the average pore size of PU foams containing different cell gases was determined. An average of three measurements was calculated in each case.

[0101] The results are summarized in the table and in Figure 4 graphically represented: Cell gas Unit No. 3.1 No. 3.2 No. 3.3 CO2 [Vol%] 100 51 32 CP [Vol%] 0 46 0 HFO 1233zd [Vol%] 0 0 65 O2 + N2 [Vol%] 0 3 3 Pore ​​size [µm] 151.0 138.1 130.6

[0102] The data clearly demonstrate the positive influence of HFO on cell size. Example 4: Determination of the flash points of the starting material

[0103] The flash points of samples No. 1 and No. 3 were determined using the Pensky-Martens method (DIN EN ISO 2719:2003-9). Sample No. 2 was measured using the Abel-Pensky method (DIN 51755). The same polyol was used in each case as in Example 1. The results are summarized in the table. component Unit No.4.1 No.4.2 No. 4.3 Polyol [g / 100 g polyol] 100 100 100 CP [g / 100 g polyol] 0 4.8 0 HFO 1233zd [g / 100 g polyol] 0 0 8.9 Flash point standardized to 1013 mbar [°C] 102.8 < - 21 > 56

[0104] Sample No. 3 has a flash point that is significantly higher than that of reference sample No. 2, which contains an equivalent molar amount of cyclopentane. In particular, sample No. 3 is not classified as flammable according to Regulation EC 440 / 2008. Example 5: Bubble formation depending on the propellant

[0105] Generally: According to Example 1, thermally insulated pipes with different cell gas compositions were manufactured.

[0106] Example 5.1 (comparative test): A quantity of cyclopentane (Cp) was added to the polyol component using a static mixer, resulting in a concentration of 7 wt% based on the polyol content. Twelve bubbles with a diameter greater than 10 mm were counted on the surface of the resulting pipe over a length of 30 cm and were easily visible without any additional aids.

[0107] Example 5.2A quantity of 2 wt% cyclopentane and 11 wt% HFO 1233zd was added to the polyol. No bubbles were detected on the surface of the pipe produced in this way over a length of 400 m.

[0108] Example 5.3: A quantity of 15 wt% HFO 1233zd was added to the polyol. No bubbles were detected on the surface of the pipe produced in this way over a length of 350 m.

[0109] Results of examples 5.1-5.3: The resulting composition of the cell gases was determined by GC as in Example 1, and the resulting tube was visually inspected. e.g. Composition of cell gas control 5.1 (Comparison) 69% Cp 12 bubbles on 0.3m length unusable 29% CO2 0% HFO 2% H2+ N2 5.2 17% Cp 0 bubbles over 400m length error-free 27% CO2 55% HFO 1% H2+ N2 5.3 0% Cp 0 bubbles over 350m length error-free 27% CO2 71% HFO 2% H2+ N2

[0110] The data show that high amounts of Cp lead to unusable insulated pipes, whereas their partial or complete replacement with HFO leads to defect-free insulated pipes.

[0111] While preferred embodiments of the invention have been described in the present specification, it is to be understood that the invention is not limited thereto and may be embodied in other ways within the scope of the following claims.

[0112] The invention is described in the following Sentences #1-#21 summarized; these are not intended to limit the invention in any way: #1.Thermally insulated pipe (1), comprising at least one carrier pipe (4), at least one thermal insulation (3) arranged around the carrier pipe and at least one outer jacket (2) arranged around the thermal insulation, characterized in that said outer jacket (2) optionally comprises a barrier (9) made of plastic, and said thermal insulation (3) comprises a foam whose cell gas contains 10-100 vol% hydrofluoroolefins (HFOs) and 0-50 vol% (cyclo)alkanes and 0-50 vol% CO 2 , and wherein said HFO is selected from the group comprising compounds of the formula (I) wherein R 5< and R 6< independently of one another represent H, F, Cl, CF 3 and wherein said alkane is selected from the group comprising propane, butanes, (cyclo)pentanes, (cyclo)hexanes and wherein said thermal insulation (3) contains a foam selected from the group of polyurethanes (PU), polyisocyanurates (PIR), thermoplastic polyesters (PET) and thermoplastic polyolefins. #2. Conduit according to #1, characterized in that said cell gas contains 10-100vol% HFOs and 0-50vol% (cyclo)alkanes and 0-50vol% CO 2 and wherein the ratio of HFOs to (cyclo)alkanes is at least 2.5:1. #3. Conduit according to one of # 1 or # 2, characterized in that said HFO is selected from the group comprising compounds of formula (I) which represent R1233zd, and / or R1336mzz. #4.Conduit according to # 1, characterized in that said thermal insulation (3) contains a foam selected from the group of polyurethanes (PU). #5. Conduit pipe according to one of # 1 to # 4, characterized in that said foam is selected from PU containing 50-100vol% R1233zd and 0-50vol% cyclopentane as cell gas; PU containing 50-100vol% R1336mzz and 0-50vol% cyclopentane as cell gas; PIR containing 50-100vol% R1233zd and 0-50vol% cyclopentane as cell gas; PIR containing 50-100vol% R1336mzz and 0-50vol% cyclopentane as cell gas; PET containing 50-100vol% R1233zd and 0-50vol% cyclopentane as cell gas; PET containing 50-100vol% R1336mzz and 0-50vol% cyclopentane as cell gas. PE containing 50-100vol% R1233zd and 0-50vol% cyclopentane as cell gas; and / or PE containing 50-100vol% R1336mzz and 0-50vol% cyclopentane as cell gas. #6.Conduit pipe according to one of # 1 to # 5, characterized in that there is a barrier (9) which is designed as a layer which reduces the diffusion of gases out of the thermal insulation and into the thermal insulation, and which enables the diffusion of water out of the thermal insulation. #7. Conduit according to one of # 1 to # 6, characterized in that the barrier (9) is arranged as a layer on the thermal insulation; and / or as a layer on the inside of the outer casing; and / or as a layer in the outer casing. #8. Conduit pipe according to one of # 1 to # 7, characterized in that the barrier (9) comprises a copolymer of ethylene and vinyl alcohol or a copolymer of ethylene and carbon monoxide or a copolymer of ethylene and carbon monoxide and propylene, and has a layer thickness of 0.05-0.5 mm. #9.Conduit according to # 8, characterized in that the polymer contains 50 - 100 wt.% structural units of formula (II) or (III) or (IV), wherein m stands for 1-10, n stands for 2-20, [with m / n 30 / 100 to 50 / 100], o stands for 1 or 2, preferably 1, p stands for 1 or 2, preferably 1, q stands for 1-20 and r stands for 1-20. #10.Conduit pipe according to one of # 1 to 9, characterized in that said carrier pipe (4) is a flexible plastic pipe, the plastic is selected from the group ABS, PEXa, PEXb, PEXc, PE, polybutene (PB), raised temperature polyethylene (PE-RT), and polyketone (PK); or a flexible plastic pipe with an outer metal layer, the plastic is selected from the group ABS, PEXa, PEXb, PEXc, PE, polybutene (PB), raised temperature polyethylene (PE-RT), and polyketone (PK), the metal is selected from the group aluminum; or a rigid plastic pipe, the plastic is selected from the group ABS, PEXa, PEXb, PEXc, PE, PB, PE-RT, and PK;or a flexible metal tube, the metal selected from the group consisting of copper including its alloys, iron including its alloys, and aluminum including its alloys; or a rigid metal tube, the metal selected from the group consisting of copper including its alloys, iron including its alloys, and aluminum including its alloys; #11. Conduit pipe according to one of # 1 to # 10, characterized in that said outer casing (2) is designed as a corrugated pipe; and said carrier pipe is designed as a flexible pipe section; or said conduit pipe is a rigid straight pipe section; or said outer casing (2) is designed as a corrugated pipe; and said carrier pipe is preferably designed as a flexible pipe section. #12 .Method for producing a thermally insulated conduit pipe, wherein said conduit pipe comprises at least one carrier pipe (4), at least one thermal insulation (3) arranged around the carrier pipe and at least one outer casing (2) arranged around the thermal insulation, wherein said outer casing (2) comprises a barrier (9) made of plastic, and wherein said thermal insulation (3) comprises a foam whose cell gas contains 10-100 vol% hydrofluoroolefins (HFOs) and 0-50 vol% (cyclo)alkanes and 0-50 vol% CO 2, in particular a conduit pipe according to one of # 1 to 11, characterized in that the thermal insulation (3) is formed by foaming a plastic composition which contains polymer components for foam formation and HFO as a blowing agent. #13.Method according to # 12, characterized in that the plastic composition comprises two liquid components, wherein the first component contains a polyol and HFO and the second component contains isocyanate; or that the plastic composition comprises two liquid components, wherein the first component contains a polyol and the second component contains isocyanate and HFO; or that the plastic composition consists of a molten component and this melt is combined with HFO under pressure. #14 .Method according to # 12 or # 13 for producing a thermally insulated conduit pipe (1) with at least one flexible carrier pipe (4), a thermal insulation layer (3) and an outer jacket (2), optionally with a barrier (9) made of plastic, wherein (e) the at least one carrier pipe is fed continuously and is covered with a plastic film shaped into a hose, (f) a foamable plastic composition is introduced into the space between the carrier pipe and the hose as a thermal insulation layer, (g) the carrier pipe and the hose are introduced into a tool formed from rotating molded parts and leave this tool at the end thereof, and then (h) the outer jacket is extruded onto the surface of the hose, characterized in that the foamable plastic composition contains the polymer component(s) for foam formation and HFO as a blowing agent. #15.Method according to # 14, characterized in that a barrier (9) is present and that the barrier is introduced between the foamed thermal insulation layer and the inside of the outer jacket by forming the tube from the polymer; or that the barrier is applied by coextrusion together with the outer jacket; or that the barrier is applied directly to the tube; or that first a layer of the outer jacket is applied, followed by the barrier and followed by at least a second layer of the outer jacket. #16.Method for producing a thermally insulated pipe (1) with at least one rigid medium pipe (4), a thermal insulation layer (3) and an outer casing (2), optionally with a barrier (9) made of plastic, wherein (a) a medium pipe is centered within an outer pipe and (b) a foamable plastic composition is introduced into the space between the medium pipe and the outer pipe as a thermal insulation layer, characterized in that the foamable plastic composition contains the polymer components for foam formation and HFO as a blowing agent. #17.Method according to # 16, characterized in that a barrier (9) is present and that a barrier is introduced between the foamed thermal insulation layer and the outside of the outer casing in the form of a hose; or that the barrier is applied to the inside of the outer pipe; or that the barrier is provided in the outer pipe; or that the barrier is applied to the outside of the outer pipe. #18. A plastic cover device or plastic sleeve for connecting thermally insulated pipes, the cover device or the sleeve comprising at least one thermal insulation (3) and at least one outer casing (2) arranged around the thermal insulation, characterized in that said outer casing (2) comprises at least one barrier (9) made of plastic, and said thermal insulation (3) comprises a foam whose cell gas contains at least 10 vol% HFOs. #19.Use of hydrofluoroolefins as cell gas for foam insulation in thermally insulated pipe systems, in particular in plastic medium pipe systems (PMR) and in plastic jacketed pipe systems (KMR), wherein said cell gas contains 10-100 vol% hydrofluoroolefins (HFOs) and 0-50 vol% (cyclo)alkanes and 0-50 vol% CO 2 , wherein said HFO is selected from the group comprising compounds of formula (I) wherein R 5< and R 6< independently of one another represent H, F, Cl, CF 3 and wherein said alkane is selected from the group comprising propane, butanes, (cyclo)pentanes, (cyclo)hexanes. #20. Use according to #18 in conduit, cover devices and / or sleeves. #21. Pipe system containing a thermal insulation, characterized in that said thermal insulation comprises a foam whose cell gas is as defined in #19.

Claims

1. A method for producing a thermally insulated conduit pipe (1), wherein said conduit pipe comprises at least one carrier pipe (4), at least one thermal insulation (3) arranged around the carrier pipe, and at least one outer jacket (2) arranged around the thermal insulation, wherein said outer jacket (2) comprises a barrier (9) made of plastic, wherein said at least one carrier pipe is a flexible carrier pipe, wherein said thermal insulation (3) comprises a foam whose cell gas contains 10-100 vol% hydrofluoroolefins (HFOs) and 0-50 vol% (cyclo)alkanes and 0-50 vol% CO2, and wherein (a) the at least one carrier pipe is continuously fed and wrapped with a plastic film formed into a tube, (b) a foamable plastic composition is introduced into the space between the carrier pipe and the tube as a thermal insulation layer,(c) the carrier pipe and the hose are introduced into a tool formed from rotating molded parts and leave this tool at its end, and then (d) the outer jacket is extruded onto the surface of the hose; and wherein the thermal insulation (3) is formed by foaming a plastic composition containing polymer components for foam formation and HFO as a blowing agent.

2. Method according to claim 1, characterized in that the plastic composition - comprises two liquid components, the first component containing a polyol and HFO and the second component containing isocyanate; or - comprises two liquid components, the first component containing a polyol and the second component containing isocyanate and HFO; or - consists of a molten component and this melt is combined with HFO under pressure.

3. Method according to claim 1 or 2, characterized in thatin step (a) the carrier pipe is continuously drawn from a supply.

4. Method according to claim 1 to 3, characterized in that in step (a) the carrier pipe is continuously produced by extrusion.

5. Method according to claim 1 to 4, characterized in that said cell gas contains 10-100vol% HFOs and 0-50vol% (cyclo)alkanes and 0-50vol% CO2 and wherein the ratio of HFOs to (cyclo)alkanes is at least 2.5:

1.

6. Method according to claim 1 to 5, characterized in that said foam is selected from - PU containing 50-100vol% R1233zd and 0-50vol% cyclopentane as cell gas; - PU containing 50-100vol% R1336mzz and 0-50vol% cyclopentane as cell gas.

7. Method according to claim 1 to 5, characterized in that said foam is selected from - PU containing 50-100vol% R1233zd and 0-50vol% cyclopentane and 0-50vol% CO2 as cell gas; - PU containing 50-100vol% R1336mzz and 0-50vol% cyclopentane and 0-50vol% CO2 as cell gas.

8. Method according to claim 1 to 7, characterized in that - the cell gases mentioned complement each other to 100 vol%, or - these cell gases together with CO2 and air complement each other to 100%.

9. The method according to claim 1 to 8, wherein said conduit comprises at least one carrier pipe (4), at least one thermal insulation (3) arranged around the carrier pipe and at least one outer jacket (2) arranged around the thermal insulation, wherein said outer jacket (2) does not comprise a barrier (9) made of plastic, wherein said at least one carrier pipe is a flexible carrier pipe, wherein said thermal insulation (3) comprises a foam whose cell gas contains 10-100 vol% hydrofluoroolefins (HFOs) and 0-50 vol% (cyclo)alkanes and 0-50 vol% CO2.

10. Method according to claim 1 to 8, characterized in that- the barrier is introduced between the foamed thermal insulation layer and the inside of the outer sheath by forming the tube from the polymer; or - the barrier is applied by coextrusion together with the outer sheath; or - the barrier is applied directly to the tube; or - first a layer of the outer sheath is applied, followed by the barrier and followed by at least a second layer of the outer sheath.