Composite pipe, and method for producing same

Abstract

The invention relates to a composite pipe (1, 11, 31) for conducting and guiding a fluid, said composite pipe comprising a stability layer (2, 12, 32) having an outer surface (3, 13, 33) and having an outer layer (4, 14, 34), the outer layer (4, 14, 34) comprising a polyolefin, characterised in that the stability layer (2, 12, 32) is silanised with at least one silane compound on the outer surface (3, 13, 33), and in that the outer layer (4, 14, 34) is adhesively bonded to the outer surface (3, 13, 33) of the stability layer (2, 12, 32) by means of the at least one silane compound. The invention also relates to a method for producing such a composite tube.

Description

[0001]June 21, 2024 Composite pipe and method for its production The invention relates to a composite pipe for conducting and guiding a fluid, comprising an internally arranged stability layer with an outer surface and an externally arranged outer layer, wherein the stability layer is silanized on the outer surface with at least one silane compound. The invention also relates to a method for producing a composite pipe and the use of a polyolefin for producing a composite pipe. Composite pipes, and in particular metal composite pipes, are widely used in plumbing to conduct water, especially drinking water, heating and cooling water, or domestic water. The corresponding composite pipes often have an aluminum layer between two plastic layers of cross-linked and / or non-cross-linked polyolefin.The composite pipes have the advantage that, unlike pure plastic pipes, they are very easy to bend and retain this shape after bending, rather than springing back to their original state. Due to the intermediate layer or stability layer made of aluminum, the pipes are impermeable to oxygen, preventing oxygen from entering the heating water, for example, and thus preventing water-side corrosion in unprotected steel parts such as radiators and boilers. Furthermore, these pipes are lighter than commonly used alternative steel or copper pipes. However, aluminum itself is not permanently corrosion-resistant, for example in plumbing or heating applications. The typical structure of a composite pipe consists of five layers, from the inside out: (1) polyolefin (2) maleic anhydride (MAH) adhesion promoter (3) aluminum (4) MAH adhesion promoter (5) polyolefin. The maleic anhydride is grafted onto a polyolefin.The MAH adhesion promoter is required because polyolefins alone practically do not adhere to materials with high surface energy, such as metals, and adhesion promoters are normally required for bonding polyolefins such as polyethylene with inorganic materials such as metals. Therefore, special, modified polyolefin types are commonly used as adhesion promoters, in which the polyolefins have been grafted with maleic anhydride. These grafted polyolefins are marketed by various manufacturers such as Mitsui Chemicals, Yparex, LyondellBasell, Silon, or Auserpolimeri under the trade names Admer, Yparex, Plexar, Tabond, and Compoline. According to current theory, ester-like bonds to the inorganic layer are formed via the anhydride group of the succinic anhydride side chain formed by the grafting.JPH 1015679 and DE 202006018466 A1 each describe such a composite pipe in which an adhesion promoter is used to bond the metal layer and the plastic layer. However, such composite pipes have the disadvantages described below. If such a composite pipe is sealed with a fitting only on the outer circumference against the fluid transported inside, the cut edge of the composite pipe inside the fitting is exposed to the medium. However, the connection between the MAH adhesion promoter (2) and (4) and the aluminum is not hydrolysis-resistant, and the aluminum is not corrosion-resistant. If the cut edge is exposed inside the fitting, the adhesion weakens over time due to the damaging effects of the fluid, especially water, and ultimately fails. This leads to collapse, in particular delamination of the inner layer, and an installation error. T / so 230312WOJune 21, 2024 It is assumed that the formed ester-like bonds are hydrolyzed, thereby removing the bond between the metal layer and the adhesion promoter layer. It is further assumed that the hydrolysis-induced delamination is self-reinforcing. During the hydrolysis of the ester-like bonds, acid groups are formed from the ester-like bonds. The acid groups increase the osmotic pressure in a moisture pocket that has formed around destroyed metal-adhesion promoter bonds. This attracts more water, causing the moisture pocket to enlarge into a bubble. This destroys further ester-like bonds of the metal-adhesion promoter bond, which in turn forms more acid groups, which, together with dissolved aluminum ions, increase the osmotic pressure. In this way, the metal-adhesion promoter bond is further destroyed, so that the polyolefin layer eventually delaminates from the metal layer.In other metal composite pipes, the aluminum pipe is replaced with a stainless steel pipe. The self-accelerating delamination described above due to adhesion promoter hydrolysis and acid-driven metal corrosion does not occur with sufficiently stable stainless steels. The stainless steel pipe is either the innermost layer in contact with the fluid, especially the water, or the stainless steel pipe represents the middle layer of the composite pipe. However, the adhesion promoter is also of the MAH type, which is why such stainless steel composite pipes must also be sealed internally. The disadvantage of an internal seal is the support sleeve inserted into the pipe as part of the fitting, which either seals itself or has grooves for O-rings. However, such internal seals always lead to undesirable pressure losses in the pipe arrangement because the flow resistance is increased.Especially in large installations, this leads to high pressure losses and the need for larger dimensions.H. T / so 230312WOJune 21, 2024 Another approach involved using perforated sheets or meshes made of stainless steel instead of aluminum strip as metal pipes, thus avoiding the use of adhesion promoters. The inner thermoplastic layer and outer thermoplastic layer are fused together in the holes of the perforated sheets or meshes, preventing the collapse of the inner plastic pipe. Such a solution is hydrolysis- and corrosion-resistant and thus hygienically suitable for external sealing. However, the technical effort involved in such a design is considerable, and the stability layer no longer functions simultaneously as a barrier layer against, for example, oxygen ingress. US 2019 / 0001625 A1 describes a coated metal surface, wherein the coating comprises a crosslinkable polymer with silane groups and a filler, in particular glass fibers.The crosslinkable silane groups of the polymer are bonded to the filler via covalent bonds. An adhesive bond to the metal surface by means of the silane compound is not present in US 2019 / 0001625 A1, since the silane groups are already consumed by crosslinking with the filler and can therefore no longer bond to the metal surface. The object of the invention is therefore to provide a composite pipe and a method that do not have the aforementioned disadvantages. Furthermore, the object of the invention is to provide a composite pipe that can be sealed across the outer diameter. Further objects, features, and advantages of the present invention will become clear from the following description. The above-described object is initially achieved by a composite pipe for conducting and guiding a fluid, in which the composite pipe has a stability layer with an outer surface and an outer layer.The outer surface is silanized with at least one silane compound. The outer layer contains a polyolefin.H. T / so 230312WOJune 21, 2024. According to the invention, the outer layer is adhesively bonded to the outer surface of the stability layer by means of the at least one silane compound. In a further embodiment of the composite pipe, an inner surface of the stability layer is silanized with at least one silane compound, wherein an inner layer is provided, wherein the inner layer contains a polyolefin, and wherein the inner layer is adhesively bonded to the inner surface of the stability layer by means of the at least one silane compound. The previously indicated object is further achieved by a composite pipe for conducting and guiding a fluid, in which the composite pipe has a stability layer with an inner surface and an inner layer. The inner layer contains a polyolefin.According to the invention, the stability layer is silanized on the inner surface with at least one silane compound, and the inner layer is adhesively bonded to the inner surface of the stability layer by means of the at least one silane compound. The outer layer and / or the inner layer contain a polyolefin. The proportion can theoretically be 100 wt.%. However, a lower proportion is also possible. The remaining proportion can, for example, comprise or consist of other polyolefins. The outer layer and / or the inner layer can also contain a grafted polyolefin, for example in a proportion of 10 wt.% or more. The grafted polyolefin can be a polyolefin grafted with a silane compound or an amine compound. Glycidyl ethers or other oxiranes, isocyanates, (meth)acrylates, and silane are also conceivable as coupling groups.It is also conceivable to coat the stability layer with tetraalkoxysilanes or, for example, sodium water glass. Particularly preferably, the composite pipe is further designed so that the stability layer contains a metallic material, in particular consists thereof. Suitable metals include, in particular, aluminum, iron, steel, stainless steel, copper, titanium, H. T / so 230312WOJune 21, 2024 Chromium, nickel, or alloys of two or more of the above metals may be used. The silane compound is preferably formed as an alkylsilane ortho acid ester, in particular C1-20 alkylsilane ortho acid ester. According to one embodiment, the silane compound is formed as an alkenylsilane ortho acid ester, in particular C2-20 alkenylsilane ortho acid ester. According to a further embodiment, the silane compound is formed as an alkynylsilane ortho acid ester, in particular C2-20 alkynylsilane ortho acid ester. The silane compound can therefore be a C1-20 alkylsilane ortho acid ester, a C2-20 alkenylsilane ortho acid ester, a C2-20 alkynylsilane ortho acid ester, or a mixture thereof. The silane compound may further be a C1-20 alkylsilane ortho acid ester or a C2-20 alkenylsilane ortho acid ester. According to a further embodiment, the silane compound is formed as a precondensate.In a precondensate, a portion of the alcoholate groups of the silane compound is hydrolyzed and condensed, so that a portion of the silane compound is present as dimers, trimers, tetramers, and / or further oligomers. Precondensates can be composed of various silane compounds, in particular various alkenylsilane orthoesters. For example, precondensates can be composed of a mixture of vinyl trialkoxy orthoesters, propyl trialkoxy orthoesters, and butyl trialkoxy orthoesters. The alkoxy groups are preferably methoxy and / or ethoxy groups. Furthermore, precondensates can be composed of tetraalkoxysilanes, for example tetramethoxysilane and tetraethoxysilane, as a further component. Corresponding precondensates can be composed of a mixture of tetramethoxysilane, tetraethoxysilane, vinyltrialkoxyorthoesters, propyltrialkoxyorthoesters and butyltrialkoxyorthoesters, wherein the alkoxy groups are preferably methoxy and / or ethoxy groups.Silanizing a surface with a silane compound refers to the chemical bonding of the silane compound to the surface. The bonding can be H. T / so 230312WOJune 21, 2024, in particular, through a condensation reaction between hydrolyzable groups of the silanes used and chemical groups on the surface, for example, hydroxyl groups. Preferably, the silanized surface of the stability layer comprises the silane compound bonded to the surface via a condensation reaction. Without wishing to be bound to any scientific theory, it is suspected that the silane compound has formed Si-O-metal bonds in a reaction with reactive groups such as oxy or hydroxyl groups of the metal surface. These Si-O-metal bonds appear to result in greater hydrolysis resistance than the ester-like bonds derived from maleic anhydride. Surprisingly, it has been found that an outer layer containing a polyolefin can form a well-adhering bond via the silane compound with which the surface of the stability layer is silanized.Depending on the type of silane compound and the polyolefin, various possibilities are conceivable for how the adhesive bond is achieved, without wishing to be bound to any scientific theory. If the surface is silanized with a silane compound containing an alkyl group, it is conceivable that the alkyl group is incorporated into the polyolefin phase, for example, the polyethylene phase, of the outer layer or the inner layer, thereby creating the adhesive bond. If the surface is silanized with a silane compound containing a reactive group such as an epoxy and the polyolefin also contains a reactive group such as an amine, for example, through grafting, it is conceivable that the reactive groups react with each other, thereby creating the adhesive bond. wird.By incorporating an alkyl group of the silane compound into the polyolefin phase of the outer layer, the adhesive bond of the stability layer with the outer layer appears to be so strong in at least some aspects that the hydrolysis resistance is largely determined by the hydrolysis stability of the Si-O-metal-H T / so 230312WOJune 21, 2024 bonds is determined. The same applies if a reactive group of the silane compound has reacted with a reactive group on the polyolefin. These Si-O-metal bonds appear to result in greater hydrolysis resistance than the ester-like bonds derived from maleic anhydride. Thus, the polyolefin-containing outer layer appears to adhere well to the stability layer, preferably a metal surface. The silane compound with which the stability layer is silanized appears to act as an adhesion promoter between the outer layer and the stability layer. In particular, in the typical structure of composite pipes described above, the silane compound appears to act as an adhesion promoter instead of the MAH. Furthermore, the hydrolysis of Si-O bonds also only produces an extremely weak acid, which at most lowers the pH slightly and does not promote the hydrolysis of further bonds.Furthermore, the silane compounds that have already formed Si-O-metal bonds can crosslink with each other, which can further increase hydrolysis resistance. This effectively counteracts delamination of the polyolefin layer from the metal surface. The maleic anhydride-grafted adhesion promoter commonly used in the prior art can be omitted. The surface of the silanized stability layer preferably has alkylsilane groups, which are schematically depicted below: , where Met stands for metal and where n is an integer from 0 to 20. In the schematic representation shown above, at the points marked with serpentine linesH T / so 230312WO21 June 2024, further molecular moieties are present, for example, alkyl radicals such as methyl groups or alkoxy groups such as methoxy groups or oxygen atoms, to which alkyl radicals or Si or Si-O groups are linked. For example, an Si-O network can form, which further increases hydrolysis stability and adhesive strength. In the composite pipe described, there is direct surface, in particular full-surface contact between the stability layer and the outer layer and / or the inner layer, without the presence of a previously customary primer, in particular MAH polyolefin, as an adhesion promoter. The outer layer and / or the inner layer thus preferably have a bond with the stability layer that is more hydrolysis-stable than with MAH polyolefin.This property has the advantage that the composite pipe can be permanently and reliably connected to an externally sealing fitting without the known and previously described problems arising due to contact with the fluid, in particular with water. The outer surface of the stability layer and / or the inner surface of the stability layer are preferably characterized as follows. Firstly, the outer surface of the stability layer and / or the inner surface of the stability layer, in particular before silanization, can have a static initial contact angle of water after 3 minutes of equilibration of 110° or less, preferably 100° or less, more preferably 90° or less. The initial contact angle is preferably determined according to DIN EN ISO 19403-2:2020-04.On the other hand, the outer layer can be attached to the outer surface of the stability layer and / or the inner layer to the inner surface of the stability layer with a peel force of at least 15 N / cm, preferably H. T / so 230312WOJune 21, 2024 at least 30 N / cm, more preferably at least 50 N / cm, adhere, determined according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min. The polyolefin contained in the outer layer and / or the polyolefin contained in the inner layer can be an ungrafted polyolefin. Furthermore, the polyolefin contained in the outer layer and / or the polyolefin contained in the inner layer can be a grafted polyolefin. For example, the polyolefin can be grafted with a silane compound, an amine compound, or an epoxy compound. A polyolefin grafted with an amine compound can be obtained, for example, by treating a polyolefin in a plasma containing NH3. Furthermore, at least one further outer layer and / or at least one further inner layer can be provided. The further outer layer and / or the further inner layer can, in particular, be a polyolefin layer.According to an advantageous embodiment, the composite pipe has at least one further outer polyolefin layer. According to a further advantageous embodiment, the composite pipe has at least one further inner polyolefin layer. The further inner polyolefin layer can be present instead of or in addition to the further outer polyolefin layer. In particular, a five-layer composite pipe can thus be formed, comprising an outer polyolefin layer, an outer layer containing a polyolefin, a stability layer, an inner layer containing a polyolefin, and an inner polyolefin layer. The polyolefin contained in the outer layer can be the same as or different from the polyolefin contained in the inner layer. The same or a different polyolefin can be used in the further outer polyolefin layer, the outer layer, the inner layer, and the further inner polyolefin layer. werden. H T / so 230312WOJune 21, 2024 The outer layer preferably has a layer thickness of 0.005 to 35 mm, more preferably from 0.01 to 7.5 mm, particularly preferably from 0.03 to 3 mm. The inner layer preferably has a layer thickness of 0.005 to 35 mm, more preferably from 0.01 to 7.5 mm, particularly preferably from 0.03 to 3 mm. The further outer layer preferably has a layer thickness of 0.5 to 30 mm, more preferably from 1 to 10 mm, particularly preferably from 1.5 to 3 mm. The further inner layer preferably has a layer thickness of 0.5 to 30 mm, more preferably from 1 to 10 mm, particularly preferably from 1.5 to 3 mm. The outer layer and / or the further outer layer preferably serve to increase the processability of the composite pipe. The outer layer and / or the further outer layer preferably do not serve as a protective layer, in particular not as a mechanical protective layer.Therefore, the outer layer and / or the further outer layer can be thin, in particular a few millimeters thick. The same applies to the inner layer and / or the further inner layer. The above-described object is also achieved according to the invention by a method in which a stability layer with an outer surface is provided, wherein the stability layer is silanized on the outer surface with at least one silane compound, and in which an outer layer is applied to the outer surface of the stability layer, wherein the outer layer contains a polyolefin. Preferably, the outer layer is applied to the stability layer by means of tube extrusion. Alternatively, the outer layer can also be applied by means of overmolding.Furthermore, an inner surface of the stability layer can be silanized with at least one silane compound and an inner layer can be applied to the inner surface of the stability layer, wherein the inner layer contains a polyolefin.H. T / so 230312WO June 21, 2024 Likewise, the above-mentioned object is also achieved by a method for producing a composite pipe, in which a stability layer with an inner surface is provided, wherein the inner surface of the stability layer is silanized with at least one silane compound, and in which an inner layer is applied to the inner surface of the stability layer, wherein the inner layer contains a polyolefin. In the method, the inner and / or the outer surface of the stability layer can be silanized with the at least one silane compound in a preceding step. werden.As described above, the silane compound can be present as a precondensate. In the process, the stability layer can be heated before and / or after the application of the inner and / or outer layer, in particular by induction heating. Preferably, the time after the application of the outer layer and the cooling process is kept long. If a composite pipe is produced with a stability layer, an outer layer, and a further outer layer, the outer layer and the further outer layer are preferably co-extruded onto the stability layer. When carrying out the previously described processes, various temperatures and / or pressures can be set. Advantageously, a temperature of 100 to 300°C, preferably 160 to 260°C, particularly preferably 200 to 260°C, is set during application. During application, a pressure of 1 to 300 bar, more preferably 10 to 200 bar, particularly preferably 50 to 150 bar, is set.This can improve adhesion.H. T / so 230312WO June 21, 2024. Preferably, when applying the outer layer and / or the inner layer, the adhesive bond is formed by the silane compound silanized onto the outer and / or inner surface of the stability layer, for example by incorporating the alkyl group into the polyolefin phase of the outer layer or by a chemical reaction of a reactive group on the silane compound with a reactive group on the polyolefin, as schematically illustrated below by way of example. Scheme: a) Application with a pressure of 100 bar and / or a temperature of 250 °C.The crosslinking of the silane groups shown in the diagram can occur before or simultaneously with the application, or in a subsequent step. For example, crosslinking can occur during a storage phase or during use of the composite pipe. In particular, the optional further crosslinking can occur in the presence of moisture in the system. Humidity is sufficient for this reaction. According to one embodiment, the outer layer and / or inner layer can be applied to the stability layer by applying the polyolefin and the silane compound as a physical mixture, optionally with the addition of a radical initiator. This can be achieved by dissolving the silane in the polyolefin in a compounding process and subsequently pelletizing the compound. This compound is then fed into the raw production line.Alternatively, in a one-step process, silane and polyolefin can be fed separately to the extruder for pipe production. In the second case, the compound is produced in situ during pipe sheet extrusion. T / so 230312WOJune 21, 2024. The previously explained methods achieve the same properties and advantages as previously described with regard to the composite pipes according to the invention and their configurations. The above-described object is also achieved by a system for creating a pipe connection with a previously described composite pipe and with an externally sealing fitting. For this purpose, the fitting preferably has a base body and a press sleeve connected thereto. The press sleeve is further preferably provided with a chamber in which a clamping ring for holding and fixing clamping elements and a sealing element are arranged. The composite pipe is inserted into the space left free by the press sleeve with the elements contained therein, for example, until it rests against a stop formed on the base body.By radially pressing the press sleeve with a suitable pressing tool, usually with two pressing jaws, the press sleeve is evenly radially deformed. This, on the one hand, brings the clamping elements into engagement with the surface of the composite pipe, thus securing the composite pipe against withdrawal from the fitting. On the other hand, the sealing element seals the outside of the composite pipe against the press sleeve and thus against the fitting. According to the invention, this allows the described composite pipe and its preferred embodiments to be connected to a fitting that only implements an externally sealing press connection. Since the composite pipe, due to the more hydrolysis-resistant bond between the polyolefin layer orSince the polyolefin layers and the stability layer form a sufficiently stable composite system, no damage occurs despite the stability layer being exposed to the fluid inside the fitting. Thus, H. T / so 230312WOJune 21, 2024, a collapse or delamination of the layers of the composite pipe and thus an installation error can be avoided. Furthermore, the above-described object is also achieved by using a previously described composite pipe in a water-conducting pipe arrangement, in particular for drinking water or heating water. The above-described object is further achieved by using a silane compound as an adhesion promoter for a bond between a polyolefin-containing layer and a stability layer, in particular a metal layer, in a composite pipe. As previously explained for the composite pipe according to the invention, the silane compound can achieve a well-adhering bond between a stability layer and a polyolefin-containing layer. The statements made herein regarding the silane compound, the polyolefin, and the stability layer apply accordingly to the silane compound, the polyolefin, and the stability layer.In the uses explained above, the same properties and advantages are achieved as previously described with regard to the composite pipes according to the invention and their configurations. Specific examples of the material configuration of the stability layer and the inner and outer layers are given below. The stability layer can contain a metallic material. The stability layer can in particular contain at least 60 wt. %, preferably at least 80 wt. %, more preferably at least 90 wt. % aluminum, iron, steel, stainless steel, copper, manganese, titanium, chromium, nickel, or alloys of two or more of these. T / so 230312WOJune 21, 2024 several of the above metals, based on the total weight of the stability layer, or consist thereof. Alternatively, the stability layer can also consist at least partially of a non-metallic material. In particular, the stability layer can contain at least 60 wt.%, preferably at least 80 wt.%, more preferably at least 90 wt.% of ceramic, ethylene-vinyl alcohol, polyvinyl alcohol, polar thermoplastics and thermosets, in particular polyamides and melamine resins, wood, cellulose, glass or mixtures thereof, preferably ethylene-vinyl alcohol, polyvinyl alcohol, polar thermoplastics and thermosets, in particular polyamides and melamine resins or mixtures thereof, based on the total weight of the stability layer, or consist thereof. It is preferably provided that the outer layer contains at least 50 wt.%, more preferably at least 70 wt.%, particularly preferably at least 90 wt.-% of the polyolefin, based on the total weight of the outer layer. The outer layer may contain an ungrafted polyolefin. The outer layer may contain a grafted polyolefin. The outer layer may contain a mixture of an ungrafted polyolefin and a grafted polyolefin. Examples of grafted polyolefins are a polyolefin grafted with a silane compound, a polyolefin grafted with an amino group, and a polyolefin grafted with an epoxy group. The outer layer may contain an ungrafted and a grafted polyolefin in different amounts. If the outer layer contains a grafted polyolefin, it is preferably present in a proportion of 1 to 100 wt.%, preferably 5 to 15 wt.%, more preferably 8 to 12 wt.%, based on the total weight of the outer layer. T / so 230312WOJune 21, 2024 To produce a polyolefin grafted with a silane compound, a silane compound can expediently be grafted to the polyolefin with the aid of a radical initiator via a carbon-carbon double bond and / or triple bond of the silane compound. For example, vinyltrimethoxysilane can be grafted to polyethylene with the aid of a radical initiator such as dibenzoyl peroxide. The polyethylene grafted with vinyltrimethoxysilane then accordingly contains 2-(trimethoxysilyl)ethyl groups. For example, a polyolefin with grafted epoxy groups can be obtained with a silane compound containing both a vinyl group and an epoxy group. Polyolefin grafted with epoxy groups, in particular polyethylene, can also be obtained by radical grafting of the polyolefin with glycidyl methacrylate. A polyolefin with grafted amine groups can be obtained by treating a polyolefin in a plasma containing NH3.A polyolefin with grafted epoxy groups can also be obtained by grafting butadiene monoxide onto the polyolefin with a radical initiator. The further outer layer can contain at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, at least 90 wt.%, or at least 99 wt.%, preferably at least 80 wt.%, more preferably at least 90 wt.%, of an ungrafted polyolefin, based on the total weight of the further outer layer. The above statements for the outer layer apply accordingly to the inner layer. The above statements for the further outer layer apply accordingly to the further inner layer. Furthermore, it can be provided that the polyolefin is composed of monomers selected from the group consisting of ethene, propene, isobutene, 1-butene, 2-butene, 4-methyl-1-pentene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, butadiene, isoprene and mixtures thereof.This applies independently to grafted and ungrafted polyolefins. In particular, the polyolefin of H. T / so 230312WOJune 21, 2024 The outer layer and / or the inner layer can be independently selected from the group consisting of polyethylene, cross-linked polyethylene, polyethylene with increased thermal resistance, polypropylene, polyisobutylene, polybutylene, polymethylpentene, polyalphaolefins, and mixtures thereof. Examples of cross-linked polyethylene are PE-Xa, PE-Xb, and PE-Xc. Polyethylene with increased thermal resistance can also be referred to as PE-RT. If polyethylene is used as the polyolefin, medium-density polyethylene is preferably used. Medium-density polyethylene can be referred to as MDPE. Advantageously, medium-density polyethylene has an average density of 0.92 g / cm3 to 0.94 g / cm3, more preferably of 0.93 g / cm3 to 0.94 g / cm3. Advantageously, medium-density polyethylene has a melting point of 125°C to 128°C. Medium density polyethylene can be used for both grafted and ungrafted polyethylene.If a grafted or ungrafted polyethylene is used in the outer and / or inner layer, medium-density polyethylene or grafted medium-density polyethylene is preferably used. If a grafted or ungrafted polyethylene is used in the further outer layer and / or the further inner layer, medium-density polyethylene or grafted medium-density polyethylene is preferably used. Medium-density polyethylene has the advantage that it supports the processability, in particular the bendability and connectability, of composite pipes and thus the laying of corresponding composite pipes. The aforementioned polyolefins, in particular polyethylene, have the advantage that their grafting with silane compounds such as vinyltrimethoxysilane is known to those skilled in the art. This allows grafted polyolefins to be produced in a simple and fundamentally known manner.Grafting can, for example, be carried out as shown schematically below:H. T / so 230312WOJune 21, 2024 Scheme: a) Radical initiator such as di-tert-butyl peroxide. The grafting of vinylsilanes and its crosslinking is known to the person skilled in the art and is described, for example, in "Polyethylene Cross-linking by Two-step Silane Method: A Review", Iranian Polymer Journal, 18 (2), 2009, 103-128. The outer layer and / or the optional additional outer layer may further contain other substances that are typically used in polyolefins, for example antioxidants, pigments, fillers, reinforcing materials, or processing aids. The same applies to the inner layer and / or the optional further inner layer. Examples of fillers are glass fibers, glass beads, calcium carbonate, talc, carbon fibers, natural fibers, polymer beads, and / or carbon black. According to one embodiment, the outer layer comprises less than 5 wt.%, preferably 3 wt.% or less, more preferably 2 wt.% or less, of fillers, based on the total weight of the outer layer.According to a further embodiment, the inner layer comprises less than 5 wt.%, preferably 3 wt.% or less, more preferably 2 wt.% or less, of fillers, based on the total weight of the inner layer. According to a preferred embodiment, the outer layer and / or the inner layer are substantially free of fillers. If the composite pipe has an outer and an inner layer, the outer layer and the inner layer are particularly preferably substantially free of fillers. T / so 230312WOJune 21, 2024, free of fillers. The same applies to the optional additional inner and / or outer layer. Specific examples of the configuration of the at least one silane compound with which the outer surface of the stability layer is silanized are described below. The same applies to the at least one silane compound of the inner surface of the stability layer. Advantageously, the silane compound can contain 1 to 30 carbon atoms, preferably 2 to 30 carbon atoms, particularly preferably 3 to 25 carbon atoms. Preferably, the silane compound has a functional group selected from the group consisting of -C1-20-alkyl, in particular -C5-20-alkyl, vinyl, -C2-20-alkynyl, -NH2, -OH, -NCO, -(CHCH2O), -OCH2(CHCH2O), -OCH3 and OC2H5, in particular from the group consisting of -C1-20-alkyl, in particular -C5-20-alkyl, vinyl, -NH2, -OH, -NCO, -(CHCH2O), -OCH2(CHCH2O), -OCH3 and OC2H5.The silane compound may contain further groups, for example alkylene groups, amine groups, ether groups, thioether groups, hydroxyl groups, epoxy groups, carbamate groups, carbonyl groups, and / or alkyl groups. The silane compound preferably contains 1 to 30, more preferably 2 to 30, and particularly preferably 3 to 25, carbon atoms and at least one functional group selected from the group consisting of -C5-20-alkyl, vinyl, propargyl, -NH2, -OH, -NCO, and -(CHCH2O), in particular from the group consisting of -C5-20-alkyl, vinyl, -NH2, -OH, -NCO, and -(CHCH2O). The silane compound advantageously has the general structural formula (I) Rod-O-Si(R2)3-mo(R3)o((CH2)nR1)m, (I). wobei m is 1 or 2,H T / so 230312WOJune 21, 2024o is 0, 1 or 2, where m and o together add up to a maximum of 3, each n is independently an integer from 0 to 10, Rod-O- denotes the bond to the stability layer, each R1 is independently -C5-20-alkyl, vinyl, propargyl, -NH2, -OH, -NCO, -(CHCH2O) or -O-CH2(CHCH2O), in particular -C5-20-alkyl, vinyl, -NH2, -OH, -NCO, -(CHCH2O) or -O-CH2(CHCH2O), each R2 is independently -O-, -OH, methoxy, ethoxy, iso-propoxy, n-propoxy, n-butoxy, sec-butoxy or iso-butoxy, or two R2 are each linked to one another by C1-5-alkylene groups, and each R3 is independently C1-4 alkyl, especially methyl or ethyl, bedeutet. In structural formula (I), a bond to a neighboring silane compound may be present via an R2, which means -O-, or a further bond to the stability layer. Preferably, in structural formula (I), n is only zero if R1 is -C5-20-alkyl bedeutet.The silane compounds with the general structural formula (I) are preferably derived from silane compounds with the structural formula (Ia)(R 3 )oSi(R 2 )4-mo ((CH2)nR 1 )m, (Ia)wherein m, n, o, R1 and R3 are as defined for the silane compounds with the general structural formula (I), m and o together add up to a maximum of 3 and each R 2 independently of one another denotes methoxy, ethoxy, iso-propoxy, n-propoxy, n-butoxy, sec-butoxy or iso-butoxy, or two or three R2 are each independently linked to one another by C1-5 alkylene groups. In a further preferred manner, the silane compound can have the structural formula (II)H T / so 230312WO June 21, 2024Stab-O-SiR22(CH2)p-R4 (II) aufweist, wobeieach R2 independently represents -O-, -OH, methoxy, ethoxy, iso-propoxy, n-propoxy, n-butoxy, sec-butoxy or iso-butoxy, or two R2 are each linked to one another by C1-5 alkylene groups, R4 represents -CH3, vinyl, C≡CH, -(CHCH2O), -O-CH2(CHCH2O), -NH2, -NCO or -OH, in particular -CH3, vinyl, -(CHCH2O), -O-CH2(CHCH2O), -NH2, -NCO or -OH, and -O- represents the bond to the stability layer, p is an integer from 0 to 20. In structural formula (II), a bond to an adjacent silane compound or a further bond to the stability layer may be present via an R2 representing -O-. According to a preferred embodiment, in structural formula (II), p is an integer from 10 to 20 and R4 is -CH3.According to a further preferred embodiment, in structural formula (II) p is an integer from 1 to 5 and R4 is -NH2, -OH, -NCO, -(CHCH2O) or -O-CH2(CHCH2O), in particular -NH2 or -O-CH2(CHCH2O).The silane compounds with the general structural formula (II) are preferably derived from silane compounds with the structural formula (IIa)R. 23Si(CH2)p-R4 (IIa) where p and R4 are as defined for the silane compounds having the general structural formula (II), and each R2 independently represents methoxy, ethoxy, iso-propoxy, n-propoxy, n-butoxy, sec-butoxy or iso-butoxy, or two or three R2 are each independently linked to one another by C1-5 alkylene groups sind. H T / so 230312WOJune 21, 2024 In a further preferred manner, it can be provided that the silane compound with which the outer and / or inner surface of the stability layer is or has been silanized is selected from the group consisting of decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, (3-isocyanatopropyl)trimethoxysilane, (3-isocyanatopropyl)triethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane. If the Polyolefin grafted with a silane compound, it can be provided in a preferred manner that the silane compound has the structural formula (III)R5rR6sSi(CH2)p-R7 (III) aufweist, wobeir is 0 or 1, s is an integer from 0 to 3, r and s together add up to a maximum of 3, p is an integer from 0 to 20, R5 is -(CHCH2O), -O-CH2(CHCH2O), -NH2, -NCO or -OH, each R6 is independently -OH, methoxy, ethoxy, iso-propoxy, n-propoxy, n-butoxy, sec-butoxy or iso-butoxy, or two R6 are each linked to one another by C1-5 alkylene groups, R7 is vinyl, propargyl, -OC(=O)-C(=CH2)H (acryloyloxy) or -OC(=O)-C(=CH2)CH3 (methacryloyloxy), in particular vinyl, -OC(=O)-C(=CH2)H (acryloyloxy) or -OC(=O)-C(=CH2)CH3 (methacryloyloxy). BEISPIEL H T / so 230312WOJune 21, 2024: An ethanol / water mixture (95 / 5; w / w) was adjusted to a pH between 4.5 and 5.5 with acetic acid. 2 wt% vinyltrimethoxysilane (Silquest A-171, supplied by Momentive), based on the weight of the ethanol / water mixture, was slowly added to the mixture with continuous stirring. This solution was sprayed onto stainless steel 1.4435 (Arinox, Italy) at room temperature and rinsed with ethanol after 5 minutes. The silane layer was formed by storage at 120°C for 30 minutes. In this way, a silanized steel sheet was prepared. erhalten.Conventional PE (Sclair 74B, supplied by Nova Chemicals) was pressed onto a silanized steel sheet prepared according to the above instructions using a platen press at a temperature of 250°C and a pressure of 120 bar for a period of 5 minutes. The peel force of the polyethylene from the steel sheet was determined to be > 50 N / cm according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min. For comparison, this test was otherwise carried out identically with non-silanized steel sheet. The peel force of the polyethylene from the steel sheet was determined to be 0 N / cm according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min. Test specimens prepared according to the previously described procedure were aged in water at 105°C. In parallel, samples were exposed to a conventional PE-gMAH-based adhesion promoter from the upper performance segment (Admer NE072 from Mitsui). The peel force was determined for comparison over the exposure time.While the PE-gMAH-based samples only showed a peel force of <2.5 N / cm according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min after 3,000 hours, the polyethylene-coated, silanized steel sheets showed a peel force of >30 N / cm according to DIN EN ISO 11339:2022-05 at H. T / so 230312WOJune 21, 2024, 25°C and 50 mm / min peel speed. No delamination was observed in the samples on silanized steel sheet. The differences in peel force retention between the PE-gMAH-based adhesion promoter system and silanized steel sheet are directly transferable to composite pipe samples produced by extrusion. The invention is explained below using exemplary embodiments with reference to the drawing. The drawing shows: Fig. 1 shows a first exemplary embodiment of a composite pipe, Fig. 2 shows a second exemplary embodiment of a composite pipe, Fig. 3 shows a third exemplary embodiment of a composite pipe, Fig. 4 shows a fourth exemplary embodiment of a composite pipe, and Fig. 5 shows an unpressed fitting for connecting a composite pipe according to Fig. 2. undFig. 6 shows the fitting with the composite pipe according to Fig. 5 in the pressed state. In the following description of the various embodiments of the invention, components and elements with the same function and the same mode of operation are provided with the same reference numerals, even if the components and elements in the various embodiments may differ in their dimensions or shape.H T / so 230312WOJune 21, 2024 Fig. 1 shows a composite pipe 1 for conducting and transporting a fluid, preferably for water in the form of drinking water or heating water. The composite pipe 1 has a stability layer 2 with an outer surface 3 and an outer layer 4. The outer surface 3 of the stability layer is silanized with at least one silane compound. The outer layer 4 contains a polyolefin. According to the invention, the outer layer 4 is adhesively bonded to the outer surface 3 of the stability layer 2 by means of the at least one silane compound with which the surface 3 is silanized. Thus, the stability layer 2 and the outer layer 4 form a firmly adhering and more hydrostable bond than with MAH adhesion promoters, without the layers being attacked by moisture penetration and the composite pipe being damaged. The outer surface 3 was silanized with an alkyltrimethoxysilane, in particular dodecyltrimethoxysilane.For the presumed mechanism, reference is made to the general description. Fig. 2 shows another composite pipe 11 with a stability layer 12 having an outer surface 13 and an inner surface 15, as well as an outer layer 14. An inner layer 16 is also provided. The outer surface 13 and the inner surface 15 are silanized with at least one silane compound. The same silane compound can be used for both surfaces, or different silane compounds can be used. Preferably, the outer surface 13 and the inner surface 15 were silanized with an alkyltrimethoxysilane, in particular dodecyltrimethoxysilane, or vinyltrimethoxysilane. The outer layer 14 contains a polyolefin and is adhesively bonded to the outer surface 13 of the stability layer 12 by means of the at least one silane compound with which the surface 13 is silanized.The inner layer 16 contains a polyolefin and the inner layer 16 is adhesively bonded to the inner surface 15 of the stability layer 12 by means of the at least one silane compound with which the inner surface 15 is silanized.H. T / so 230312WOJune 21, 2024 Thus, the inner layer 16 is bonded to the stability layer 12 via the inner surface 15 with greater hydrolysis stability than with an MAH bonding agent. For an explanation of this bond, reference is made to the general part of the description. Fig. 3 shows a further embodiment of a composite pipe 21 for conducting and guiding a fluid. In this embodiment, a stability layer 22 and an inner layer 26 are provided. An outer layer as in the embodiments according to Figs. 1 and 2 is not present. The inner surface 25 of the stability layer 22 is silanized with at least one silane compound. The inner surface 25 was preferably silanized with an alkyltrimethoxysilane, in particular dodecyltrimethoxysilane, or vinyltrimethoxysilane. The inner layer 26 contains a polyolefin.Furthermore, the inner layer 26 is adhesively bonded to the inner surface 25 of the stability layer 22 by means of the at least one silane compound with which the inner surface 25 is silanized. Thus, the inner layer 26 is bonded to the stability layer 22 via the inner surface 25 with greater hydrolysis stability than with an MAH adhesion promoter. For an explanation of this bond, reference is made to the general part of the description. Fig. 4 shows another composite pipe 31 with a stability layer 32 with an outer surface 33 and with an outer layer 34. The outer surface 33 is silanized with at least one silane compound. The outer surface 33 was preferably silanized with an alkyltrimethoxysilane, in particular dodecyltrimethoxysilane, or vinyltrimethoxysilane. The outer layer 34 contains a polyolefin.Furthermore, the composite pipe 31 has a further outer polyolefin layer 37 which is connected to the outer layer 34 via the outer surface 38 of the outer layer 34.H. T / so 230312WOJune 21, 2024. According to the invention, the outer layer 34 is adhesively bonded to the outer surface 33 of the stability layer 32 by means of the at least one silane compound with which the outer surface 33 is silanized. Thus, the stability layer 32 and the outer layer 34 form a firmly adhering and more hydrostable bond than with MAH adhesion promoter, without the layers being attacked by moisture penetration and the composite pipe being damaged. Reference is made to the general description for the presumed mechanism. The further outer polyolefin layer 37 adheres to the outer layer 34 via mechanisms known to those skilled in the art. In the embodiments shown in Figs. 1 to 4, the stability layer 2, 12, 22, 32 contains a metallic material; in particular, the stability layer consists of a metallic material. The use of copper and aluminum is preferred.The outer layer 4, 14, 34 and / or the inner layer 16, 26 comprise a proportion of a polyolefin, preferably more than 80% by weight, based on the weight of the outer layer or the inner layer. The outer layer 4, 14, 34 and / or the inner layer 16, 26 may additionally comprise a polyolefin grafted with a silane compound, for example, a portion of PEX-b. Furthermore, the outer layer 4, 14, 34 adheres to the outer surface 3, 13, 33 of the stability layer 2, 12, 32 and / or the inner layer 16, 26 adheres to the inner surface 15, 25 of the stability layer 12, 22 with a peel force of at least 15 N / cm, determined according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min. Figs. 5 and 6 show a system for creating a pipe connection, with a composite pipe 11, as shown in Fig. 4, and an externally sealing fitting. 40. H T / so 230312WOJune 21, 2024 The fitting 40 has a base body 44 and an inwardly projecting stop element 45 formed circumferentially in the base body 44. Furthermore, a compression sleeve 41 is provided, which is connected to the base body 44 and forms an outer contour 42 and has a chamber 43 directed inward toward the pipe 11 to be received. A clamping ring 46 made of a plastic material with a plurality of clamping elements 47 oriented counter to the extension direction of the pipe 31 to be inserted is arranged in the chamber 43. Furthermore, a sealing element 48 is arranged in the chamber 43 adjacent to the stop element 45. The compression sleeve 41 is integrally connected to the base body 44, so that the compression section in the form of the compression sleeve 41 and the base body 44 can advantageously be manufactured as a single piece.The pipe 31 is secured against pullout and / or excessive internal pressure by the clamping ring 46, which is designed as a plastic clamping ring and in which metallic cutting edges are arranged as clamping elements 47. The plastic clamping ring 46 also has circumferential slots that make the clamping ring 46 flexible overall and thus facilitate installation in the fitting 40 within the compression sleeve 41. The clamping elements 47 are designed as cutting edges in the form of wire elements that are inserted into recesses provided for this purpose. The clamping elements 47 are thus fixed in the plastic of the clamping ring 46 in a form-fitting manner. The clamping elements 47 can be manufactured in various ways, for example as cast parts or as stamped parts. The number of clamping elements 47 is six in the present case, but can be determined depending on the requirements or dimensions of the clamping ring 47.The clamping elements 47 are further arranged in the distal region of the chamber 43 opposite the stop elements 45 and absorb the pull-out force by the clamping elements 47 selectively deforming the tube 31,H. T / so 230312WOJune 21, 2024 (see Fig. 6), and are supported on the wall in a distal outer corner area 41a of the compression sleeve 41. This ensures a direct flow of force from the pipe 31 via the compression sleeve 41 into the fitting 40. After pressing, the clamping ring 46 has only a supporting function and contributes little or nothing to the pull-out protection. The pressing process becomes clear by comparing Figs. 5 and 6. By a radially inward movement of the pressing jaw halves (not shown) and by the contact of the pressing jaw halves with the compression sleeve 41, the compression sleeve 41 is deformed radially inward. This deforms the clamping ring 46 in such a way that the clamping elements 47 press inward into the material of the pipe 31, thus securing the pipe 31 to the fitting 40.On the other hand, when the compression sleeve 41 is deformed, the seal 48 is also deformed radially inward, and the seal 48 seals against the pipe 31 and the compression sleeve 41. As explained above, an important advantage of the designs of the composite pipe 31—as well as the other described composite pipes 1, 11, and 21—is that the outer layer 34 is adhesively bonded to the stability layer 32 by means of the at least one silane compound with which the outer surface 33 of the stability layer 32 is silanized, whereby a more hydrolysis-resistant bond is present between the stability layer 32 and the outer layer 34 than with an MAH adhesion promoter. As a result, as shown in Fig.6, through the connection between the composite pipe 31 and the fitting 40, which is only pressed from the outside, the end surface 39 of the composite pipe 131 can come into unprotected contact with the medium, such as water, carried in the pipe 31 and the fitting 40, without hydrolysis-related damage to the layers 32, 34 and 37 occurring. The described design of the composite pipe 31 therefore makes it possible to achieve a T / so 230312WO 21 June 2024 pipe inside pressing with the help of a conventional support body is omitted werden. The advantage then lies in the fact that the cross-section of the connection of the composite pipe 31 through the fitting 40 with a support body is avoided. Lower pressure losses in a pipe arrangement are thus achieved.H T / so 230312WO June 21, 2024

Claims

June 21, 2024 Patent Claims 1. Composite pipe (1, 11, 31) for conducting and guiding a fluid, - with a stability layer (2, 12, 32) with an outer surface (3, 13, 33)u nd- with an outer layer (4, 14, 34), wherein the outer layer (4, 14, 34) contains a polyolefin, characterized in that - the stability layer (2, 12, 32) is silanized on the outer surface (3, 13, 33) with at least one silane compound and - that the outer layer (4, 14, 34) is adhesively bonded to the outer surface (3, 13, 33) of the stability layer (2, 12, 32) by means of the at least one silane compound.

2. Composite pipe (11) according to claim 1, characterized in that - the stability layer (12) is silanized on an inner surface (15) with at least one silane compound, - that an inner layer (16) is provided, wherein the inner layer contains a polyolefin, and - that the inner layer (16) is adhesively connected to the inner surface (15) of the stability layer (12) by means of the at least one silane compound.3.Composite pipe (21) for conducting and guiding a fluid,- with a stability layer (22) with an inner surface (25) and- with an inner layer (26),- wherein the inner layer (26) contains a polyolefin,characterized in that. - 2 -- that the stability layer (22) is silanized on the inner surface (25) with at least one silane compound and that the inner layer (26) is adhesively bonded to the inner surface (25) of the stability layer (22) by means of the at least one silane compound.

4. Composite pipe (1, 11, 21, 31) according to one of claims 1 to 3, characterized in that the stability layer (2, 12, 22, 32) contains a metallic material, in particular consists thereof.

5. Composite pipe (1, 11, 21, 31) according to one of claims 1 to 4, characterized in that the stability layer (2, 12, 22, 32) consists at least partially of a non-metallic material.6.Composite pipe (1, 11, 21, 31) according to one of claims 1 to 5, characterized in that the outer layer (4, 14, 34) adheres to the outer surface (3, 13, 33) of the stability layer (2, 12, 32) and / or the inner layer (16, 26) adheres to the inner surface (15, 25) of the stability layer (12, 22) with a peel force of at least 15 N / cm, preferably at least 30 N / cm, more preferably at least 50 N / cm, determined according to DIN EN ISO 11339:2022-05 at 25°C and a peel speed of 50 mm / min.

7. Composite pipe (1, 11, 21, 31) according to one of claims 1 to 6, characterized in that the polyolefin contained in the outer layer (4, 14, 34) and / or the polyolefin contained in the inner layer (16, 26) is a grafted polyolefin.

8. Composite pipe (1, 11, 21, 31) according to one of claims 1 to 7, characterized in that H. T / so 230312WO June 21, 2024 - 3 - that at least one further outer layer, in particular at least one further outer polyolefin layer (37), and / or at least one further inner layer, in particular at least one further inner polyolefin layer, is provided.

9. A method for producing a composite pipe (1, 11, 31) according to one of the preceding claims,- in which a stability layer (2, 12, 32) with an outer surface (3, 13, 33) is provided, wherein the stability layer is silanized on the outer surface (3, 13, 33) with at least one silane compound, and- in which an outer layer (4, 14, 34) is applied to the outer surface (3, 13, 33) of the stability layer (2, 12, 32),- wherein the outer layer (4, 14, 34) contains a polyolefin.

10. Method according to claim 9, wherein the outer layer (4, 14, 34) is applied to the stability layer (2, 12, 32) by means of tube extrusion.11.Method according to claim 9 or 10, wherein an inner surface (15) of the stability layer (12) is silanized with at least one silane compound, and wherein an inner layer (16) is applied to the inner surface (15) of the stability layer (12), wherein the inner layer (16) contains a polyolefin.

12. Method for producing a composite pipe (21) according to one of claims 3. bis 8, - in which a stability layer (22) having an inner surface (25) is provided, wherein the inner surface (25) of the stability layer (22) is silanized with at least one silane compound, andH T / so 230312WO June 21, 2024 - 4 -- in which an inner layer (26) is applied to the inner surface (25) of the stability layer (22), - wherein the inner layer (26) contains a polyolefin.

13. Method according to one of claims 9 to 12, in which the stability layer (2, 12, 22, 32) is heated before and / or after the application of the inner (16, 26) and / or the outer layer (4, 14, 34), in particular by induction heating.

14. System for creating a line connection, - with a composite pipe (1, 11, 21, 31) according to one of the preceding claims nsprüche und - with an externally sealing fitting (40).

15. Use of a composite pipe (1, 11, 21, 31) according to one of the preceding claims in a water-conducting pipe arrangement, in particular for drinking water or heating water.

16. Use of a silane compound as an adhesion promoter for a connection of a polyolefin-containing layer to a stability layer, in particular a metal layer, in a composite pipe. H T / so 230312WO June 21, 2024

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