Composite pipe and method for manufacturing composite pipe

Abstract

The present invention relates to a composite tube (1, 11) for guiding and directing a fluid, comprising a stabilizing layer (2, 12) having an outer surface (3, 13) and an outer layer (4, 14) containing a polyolefin grafted with at least one silane compound, wherein the outer layer (4, 14) is bonded to the outer surface (3, 13) of the stabilizing layer (2, 12) by at least one silane compound of the grafted polyolefin. The present invention also relates to a method for manufacturing such a composite tube.

Description

[Technical Field]

[0001] The present invention relates to a composite tube for guiding and directing fluids, comprising an internally positioned stabilizing layer having an external surface, and an externally positioned outer layer, wherein the outer layer at least partially contains a polyolefin grafted with a silane compound. The present invention also relates to a method for manufacturing a composite tube and the use of polyolefins in the manufacture of a composite tube.

[0002] Composite pipes, particularly metal composite pipes, are widely used in pipeline installations to guide water, especially drinking water, heated water, or industrial water. In this case, the corresponding composite pipes often have an aluminum layer between two plastic layers made of cross-linked or non-cross-linked polyolefins.

[0003] Here, composite tubes, unlike pure plastic tubes, have the advantage of being very easy to bend, retaining their shape after bending, and not springing back to their original state. In addition, the intermediate or stabilizing layer made of aluminum makes the tube impermeable to oxygen, so there is no oxygen intrusion into hot water, for example, and no water-side corrosion in unprotected steel components such as radiators and boilers. Furthermore, these tubes are lighter than the steel or copper tubes that are often used as alternatives. However, aluminum itself is not corrosion-resistant in the long term, for example, in sanitary or heating applications.

[0004] A typical composite tube consists of five layers, from inside to outside: (1) polyolefin, (2) maleic anhydride (MAH) fixative, (3) aluminum, (4) MAH fixative, and (5) polyolefin. Here, the maleic anhydride is grafted onto the polyolefin.

[0005] Polyolefins alone do not substantially adhere to materials with high surface energy, such as metals. Bonding polyolefins such as polyethylene to inorganic materials such as metals usually requires a fixative, hence the need for MAH fixatives. Therefore, a special type of modified polyolefin, grafted with maleic anhydride, is typically used as the fixative. This grafted polyolefin is sold by various manufacturers, including Mitsui Chemicals, Yparex, LyondellBasell, Silon, and Auserpolimeri, under trade names such as Admer®, Yparex®, Plexar, Tabond, and Compoline. According to general theory, in this case, an ester-like bond is formed with the inorganic layer via the anhydride groups of the succinic anhydride side chains produced by grafting.

[0006] Patent documents 1 and 2 describe composite tubes in which a fixing agent is used to bond a metal layer and a plastic layer, respectively. However, such composite tubes have the following drawbacks.

[0007] If such a composite pipe is sealed only at its outer circumference with fittings to the fluid being transported inside, the cut edges of the composite pipe are exposed to the medium within the fittings. However, the bond between the MAH fixing agents (2) and (4) and aluminum is not hydrolyzable, and aluminum is not corrosion-resistant. When the cut edges are exposed within the fittings, the detrimental effect of the fluid, especially water, weakens the adhesion over time, eventually leading to its loss. This results in collapse, particularly delamination of the inner layers, and defects in the equipment.

[0008] It is presumed that the ester-like bonds formed are hydrolyzed, causing the bond between the metal layer and the fixing agent layer to be lost.

[0009] Furthermore, the delamination due to hydrolysis is presumed to be self-amplifying, because acidic groups are formed from the ester-like bonds during hydrolysis. These acidic groups increase the osmotic pressure in the moisture pockets formed around the destroyed metal-fixing bonds. This attracts more water, causing the moisture pockets to expand and form bubbles. This further destroys the ester-like bonds of the metal-fixing bonds, forming even more acidic groups, which, along with the dissolved aluminum ions, increase the osmotic pressure. In this way, the metal-fixing bonds continue to break down, and eventually the polyolefin layer delaminates from the metal layer.

[0010] In other metal composite tubes, aluminum tubes are replaced with stainless steel tubes. The self-accelerating delamination caused by hydrolysis of the fixing agent and metal corrosion by acid does not occur in sufficiently stable stainless steel. In this case, the stainless steel tube is either the innermost layer in contact with the fluid, especially water, or the stainless steel tube is an intermediate layer in the composite tube. However, since the fixing agent is of the MAH type, such stainless steel composite tubes also need to be internally sealed.

[0011] The drawback of internal seals lies in the support sleeve inserted into the pipe as part of the fitting, which is either self-sealing or has a groove for an O-ring. However, such internal seals increase flow resistance, resulting in undesirable pressure loss in pipeline assemblies. In particular, in large-scale installations, this can lead to excessively large pressure loss, requiring larger dimensions.

[0012] Another approach was to avoid using fixing agents by using a perforated sheet or mesh made of stainless steel instead of an aluminum strip as the metal tube. The inner thermoplastic layer and the outer thermoplastic layer fused with each other inside the holes of the perforated sheet or mesh, thereby preventing the collapse of the inner plastic tube. Such a solution is hygienically suitable for external seals because it has hydrolysis resistance and corrosion resistance. However, in such an embodiment, the technical effort is considerable, and the stabilizing layer does not function simultaneously as a barrier layer against, for example, oxygen ingress in this structural method.

[0013] Patent Document 3 describes a coated metal surface, and this coating contains a crosslinkable polymer having a silane group and a filler, particularly glass fiber. Here, the crosslinkable silane group of the polymer is bonded to the filler via a covalent bond. Since the silane group has already been consumed by crosslinking with the filler and can no longer bond to the metal surface, the adhesion bonding of the silane compound to the metal surface is not described in Patent Document 3.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Patent Document 2

Patent Document 3

[0015] Therefore, the object of the present invention is to provide a composite pipe and a method that do not have the above-mentioned drawbacks. Furthermore, the object of the present invention is to provide a composite pipe that can be sealed over its outer diameter. Further objects, features, and advantages of the present invention will become apparent from the following description.

[0016] The aforementioned problem is first solved by a composite pipe for guiding and guiding fluids, which has a stable layer with an outer surface and an outer layer. The outer layer contains a polyolefin grafted with at least one silane compound. According to the present invention, the outer layer is adhesively bonded to the outer surface of the stable layer by at least one silane compound of the grafted polyolefin.

[0017] In a further form of the composite pipe, an inner layer containing a polyolefin grafted with at least one silane compound is provided, and the inner layer is adhesively bonded to the inner surface of the stable layer by at least one silane compound of the grafted polyolefin.

[0018] The aforementioned problem is further solved by a composite pipe for guiding and guiding fluids, which includes a stable layer and an inner layer. The inner layer contains a polyolefin grafted with a silane compound. According to the present invention, the inner layer is adhesively bonded to the inner surface of the stable layer by at least one silane compound of the grafted polyolefin.

[0019] The outer layer and / or the inner layer contains a polyolefin grafted with a silane compound in a certain proportion. The proportion can theoretically be 100% by weight. However, a lower proportion of 10% by weight is preferred. The remaining proportion may, for example, contain or consist of one or more non-grafted polyolefins.

[0020] Particularly preferably, the composite pipe further has a stable layer containing a metal material and is particularly formed of a metal material. As the metal, in particular, aluminum, iron, steel, stainless steel, copper, titanium, chromium, nickel, or an alloy of the above metals can be used.

[0021] To produce polyolefins grafted with silane compounds, it is convenient to use a radical initiator to graft the silane compound onto the polyolefin via the carbon-carbon double and / or triple bonds of the silane compound. For example, vinyltrimethoxysilane can be grafted onto polyethylene using a radical initiator such as dibenzoyl peroxide. Polyethylene grafted with vinyltrimethoxysilane correspondingly has a 2-(trimethoxysilyl)ethyl group.

[0022] Silane compounds on grafted polyolefins can react with, for example, hydroxyl groups to form bonds via silicon atoms or oxygen atoms bonded to silicon atoms. This reaction can be accelerated using crosslinking catalysts, particularly dibutyltin dilaurate, tin(II) acetate, tin(II) octoate, dibutyltin dioctoate, dioctyltin bis(isooctylthioglycolate), and / or bismuth(III) neodecanoate. However, it is preferable not to use crosslinking catalysts when creating adhesion to the stable layer. Advantageously, the outer layer is bonded to the outer surface of the stable layer by at least one silane compound of the grafted polyolefin without the use of a crosslinking catalyst. Advantageously, the inner layer is bonded to the inner surface of the stable layer by at least one silane compound of the grafted polyolefin without the use of a crosslinking catalyst.

[0023] It is preferable that the silane compound on the grafted polyolefin does not react at the silicon atoms before being deposited on the stable layer. The silane compound is preferably an alkylsilane orthoate ester, particularly C 2~11 It is formed as an alkylsilane orthoate ester. Before grafting, the silane compound is preferably an alkenylsilane orthoate ester, particularly C 2~11 Alkenylsilane orthoate (C 2-11It is formed as an alkenylsilansaeureorthoester. For example, vinyltrimethoxysilane can be grafted onto a polyolefin, thereby allowing the 2-(trimethoxysilyl)ethyl group to react and form a new bond via the silicon atom.

[0024] According to another embodiment, the silane compound on the grafted polyolefin is preferably an alkenylsilane orthoate ester, particularly C 2~11 It is formed as an alkenylsilane orthoate ester. According to this embodiment, the silane compound is preferably an alkynylsilane orthoate ester, particularly C, before grafting. 2~11 Alkinylsilane orthoate (C 2-11 It is formed as an Alkinylsilansaeureorthoester.

[0025] According to another embodiment, the silane compound is preferably formed as a precondensate (Vorkondensat) before grafting. In the precondensate, some of the alkole groups of the silane compound undergo hydrolysis and condensation, so that some of the silane compound exists as dimers, trimers, tetramers and / or further oligomers. The precondensate can consist of various silane compounds, particularly various alkenylsilane orthoesters. For example, the precondensate may consist 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, the precondensate may consist of tetraalkoxysilanes as further components, such as tetramethoxysilane and tetraethoxysilane. A suitable precondensate can consist of a mixture of tetramethoxysilane, tetraethoxysilane, vinyl trialkoxy orthoesters, propyl trialkoxy orthoesters and butyl trialkoxy orthoesters, where the alkoxy groups are preferably methoxy and / or ethoxy groups.

[0026] When a polyolefin grafted with a silane compound is deposited onto a stable layer, the silane compound grafted onto the polyolefin achieves adhesive bonding between the grafted polyolefin and the stable layer. Surprisingly, it was found that much better adhesive bonding was obtained when the deposition was performed without the use of a crosslinking-promoting catalyst. Therefore, it is preferable to bond the stable layer to the outer layer containing the polyolefin grafted with a silane compound without using a crosslinking-promoting catalyst.

[0027] While we do not wish to be bound by any particular scientific theory, it is presumed that the silane compound on the grafted polyolefin reacts with reactive groups such as hydroxyl groups on the metal surface to form Si-O metallic bonds. These Si-O metallic bonds appear to provide higher hydrolysis resistance than the ester-like bonds derived from maleic anhydride. Thus, the polyolefin grafted with the silane compound appears to adhere well to the metal surface. The polyolefin grafted with the silane compound appears to act as a fixative between the outer layer and the stabilizing layer. In particular, the grafted silane compound appears to act as a fixative in place of MAH in the typical composite tube structure described at the beginning.

[0028] Furthermore, hydrolysis of Si-O bonds produces only extremely weak acids, slightly lowering the pH value and not promoting further hydrolysis of the bonds. Moreover, silane compounds that already form Si-O metallic bonds can be crosslinked with each other, further enhancing their hydrolysis resistance. This effectively prevents the peeling of the polyolefin layer from the metal surface. The maleic anhydride grafting fixative commonly used in conventional technologies may become unnecessary.

[0029] Preferably, a Si-O-Met type bond exists between the outer layer and the stable layer, where Met represents a metal. The metal is selected from the metals mentioned above. This is schematically shown below. [ka] In the formula, n is an integer from 0 to 10, preferably 1. In the schematic diagram above, the areas represented by the dashed lines contain further molecular parts, such as alkyl residues like methyl groups, alkoxy groups like methoxy groups, or oxygen atoms, to which alkyl residues, Si groups, or Si-O groups are bonded. In this way, for example, an Si-O network can be formed that further enhances hydrolysis stability.

[0030] In the composite tube described, there is direct surface contact, particularly full surface contact, between the stabilizing layer and the outer and / or inner layers without the presence of conventional primers such as MAH-polyolefins as fixing agents. This strong bond is preferably achieved without the use of catalysts, particularly dibutyltin dilaurate, tin(II) acetate, tin(II) octoate, dibutyltin dioctoate, dioctyltin bis(isooctylthioglycolate) and / or bismuth(III) neodecanoate.

[0031] Therefore, the outer and / or inner layers preferably have a bond with a stable layer that has higher hydrolysis stability than when MAH-polyolefin is used. This property has the advantage that the composite tube can be permanently and reliably bonded to the fitting for the outer seal without causing the above known problems resulting from contact with fluids, especially water.

[0032] The outer surface and / or inner surface of the stabilizing layer are preferably characterized as follows:

[0033] Firstly, the outer surface and / or inner surface of the stabilizing layer may have a static initial contact angle of 110° or less, preferably 100° or less, and more preferably 90° or less, of water after equilibration for 3 minutes. Here, the initial contact angle is preferably determined in accordance with DIN EN ISO 19403-2:2020-04.

[0034] Secondly, the outer layer may adhere to the outer surface of the stabilizing layer and / or the inner layer may adhere to the inner surface of the stabilizing layer with a peeling force of at least 15 N / cm, preferably at least 30 N / cm, and more preferably at least 50 N / cm, determined in accordance with DIN EN ISO 11339:2022-05 at 25°C and a peeling rate of 50 mm / min.

[0035] Furthermore, at least one further outer layer and / or at least one further inner layer may be provided. The further outer layer and / or further inner layer may be, in particular, a polyolefin layer. According to an advantageous embodiment, the composite tube has at least one further outer polyolefin layer. According to another advantageous embodiment, the composite tube has at least one further inner polyolefin layer. The further inner polyolefin layer may be present instead of or in addition to the further outer polyolefin layer. In particular, thus a five-layer composite tube can be formed, comprising an outer polyolefin layer, an outer layer containing a polyolefin grafted with at least one silane compound, a stabilizing layer, an inner layer containing a polyolefin grafted with at least one silane compound, and an inner polyolefin layer.

[0036] The polyolefin grafted with at least one silane compound contained in the outer layer may be the same as, or different from, the polyolefin grafted with at least one silane compound contained in the inner layer.

[0037] The outer layer preferably has a thickness of 0.005 to 35 mm, more preferably 0.01 to 7.5 mm, and particularly preferably 0.03 to 3 mm. The inner layer preferably has a thickness of 0.005 to 35 mm, more preferably 0.01 to 7.5 mm, and particularly preferably 0.03 to 3 mm. The further outer layer preferably has a thickness of 0.5 to 30 mm, more preferably 1 to 10 mm, and particularly preferably 1.5 to 3 mm. The further inner layer preferably has a thickness of 0.5 to 30 mm, more preferably 1 to 10 mm, and particularly preferably 1.5 to 3 mm.

[0038] The outer layer and / or further outer layers preferably serve to improve the processability of the composite tube. The outer layer and / or further outer layers preferably do not function as protective layers, particularly mechanical protective layers. Therefore, the outer layer and / or further outer layers can be thin, especially to a few millimeters. The same applies to the inner layer and / or further inner layers.

[0039] The above problems can also be solved by a method according to the present invention, which involves preparing a stable layer having an outer surface, and applying an outer layer containing a polyolefin grafted with at least a silane compound to the outer surface of the stable layer.

[0040] Preferably, the outer layer is attached to the stabilizing layer by tube extrusion. Alternatively, the outer layer can also be attached by injection molding of the material.

[0041] Furthermore, an inner layer containing a polyolefin grafted with at least one silane compound can be applied to the inner surface of the stable layer.

[0042] Similarly, the above problems can also be solved by a method for producing a composite tube, which involves preparing a stable layer having an inner surface, and then depositing an inner layer containing a polyolefin grafted with at least one silane compound onto the inner surface of the stable layer.

[0043] In this method, the stabilizing layer can be heated, particularly by induction heating, before and / or after the deposition of the inner and / or outer layers. Preferably, the time after deposition of the outer layer and the cooling process are extended.

[0044] Preferably, the inner and / or outer layers are coated without the use of a crosslinking-promoting catalyst.

[0045] When manufacturing a composite tube comprising a stabilizing layer, an outer layer, and a further outer layer, the outer layer and the further outer layer are preferably co-extruded onto the stabilizing layer.

[0046] When carrying out the above method, various temperatures and / or pressures can be set. Advantageously, the temperature at the time of adhesion is set to 100-300°C, preferably 160-260°C, and particularly preferably 200-260°C. The pressure at the time of adhesion is set to preferably 1-300 bar, more preferably 10-200 bar, and particularly preferably 50-150 bar. This can improve adhesion.

[0047] Preferably, when the outer and / or inner layers are deposited, covalent bonds are formed by polyolefins grafted with silane compounds, as schematically shown in the following example.

[0048] [ka] Scheme: a) Deposition at a pressure of 100 bar and / or a temperature of 250°C. b) Influence of water.

[0049] Any further crosslinking in step b) shown in the scheme may be performed simultaneously with the bonding or in subsequent steps as shown in the scheme. For example, crosslinking may occur during the storage phase or during the use of the composite tube. In particular, any further crosslinking may occur in the presence of moisture in the system.

[0050] According to one embodiment, the outer and / or inner layers can be deposited onto the stable layer by physically mixing polyolefin and silane compounds without prior grafting, and optionally adding a radical initiator to adhere to the stable layer. This can be achieved by dissolving silane in the polyolefin during the compounding process, and then pelletizing the compound. The compound is then sent to semi-finished product manufacturing. Alternatively, in a one-step process, the silane and polyolefin may be fed separately to the extruder for semi-finished product manufacturing. In the latter case, the compound is manufactured in situ during the extrusion of the tubular layer.

[0051] The method described above achieves the same characteristics and advantages as those previously mentioned with respect to the composite tube and its form according to the present invention.

[0052] The above problems can also be solved by a system for forming a pipeline connection, which comprises the composite pipe described above and a fitting for an external seal.

[0053] For this purpose, the joint preferably comprises a base and a press sleeve coupled thereto. The press sleeve further preferably comprises a chamber in which a clamping ring for holding and securing a clamping element and a sealing element are arranged. The composite pipe is inserted into the space created by the press sleeve and the elements housed therein until it strikes, for example, a stopper formed in the base. The press sleeve is uniformly deformed radially by pressing it radially with a suitable press tool, which generally has two press jaws. This prevents the composite pipe from being pulled out of the joint, on the one hand, by the clamping element engaging with the surface of the composite pipe. On the other hand, the sealing element seals the outside of the composite pipe to the press sleeve and, consequently, to the joint.

[0054] Thus, according to the present invention, the composite pipe and its preferred embodiment can be coupled with a joint that achieves only an externally sealed press joint. The composite pipe is a sufficiently stable composite system due to the more hydrolysis-resistant bonding between one or more polyolefin layers and a stabilizing layer, so that even if fluid inside the joint comes into contact with the end face of the stabilizing layer, no damage occurs. This prevents the collapse or delamination of the layers of the composite pipe and, consequently, defects in the equipment.

[0055] Furthermore, the above-mentioned problems can also be solved by using the composite pipes described above, particularly in water conduit assemblies for drinking water or hot water.

[0056] Similarly, the above problems can also be solved by using a layer containing polyolefins grafted with a silane compound in a composite tube for hydrolysis-resistant bonding between layers, particularly polyolefin-containing layers, and stabilizing layers, particularly metal-containing stabilizing layers.

[0057] The above problems can be further solved by using polyolefins grafted with silane compounds as a fixative for bonding the polyolefin-containing layer to the stabilizing layer, particularly the metal layer.

[0058] As described above, with respect to the composite tube according to the present invention, good adhesion bonding with the stable layer can be achieved by grafting polyolefin silane compounds.

[0059] The polyolefins, polyolefins, and stabilizers grafted with this silane compound are subject to the provisions herein relating to polyolefins, polyolefins, and stabilizers grafted with silane compounds.

[0060] In the use described above, the same characteristics and advantages as those previously described with respect to composite tubes and their embodiments according to the present invention are achieved.

[0061] The following are specific examples of the material composition of the stabilizing layer, as well as the inner and outer layers.

[0062] The stabilizing layer may contain a metallic material. In particular, the stabilizing layer may contain, or consist of, at least 60% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight of aluminum, iron, steel, stainless steel, copper, manganese, titanium, chromium, nickel, or an alloy of two or more of the above metals, based on the total weight of the stabilizing layer.

[0063] Alternatively, the stabilizing layer may consist of at least partially nonmetallic material. In particular, the stabilizing layer may contain, or consist of, at least 60% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight of ceramic, ethylene vinyl alcohol, polyvinyl alcohol, polar thermoplastic resin and duromer, especially polyamide and melamine resin, wood, cellulose, glass, or mixtures thereof, preferably ethylene vinyl alcohol, polyvinyl alcohol, polar thermoplastic resin and duromer, especially polyamide and melamine resin, or mixtures thereof, based on the total weight of the stabilizing layer.

[0064] Preferably, the outer layer is specified to contain polyolefin grafted with a silane compound in an amount of at least 1% by weight, at least 10% by weight, at least 20% by weight, at least 30% by weight, at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, or at least 90% by weight, preferably at least 10% by weight, relative to the total weight of the outer layer. In particular, the outer layer may contain polyolefin grafted with a silane compound in an amount of 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight, and especially preferably 8 to 12% by weight, relative to the total weight of the outer layer.

[0065] The outer layer may contain ungrafted polyolefins in addition to polyolefins grafted with silane compounds. The outer layer can contain ungrafted polyolefins in various amounts.

[0066] Preferably, the outer layer contains at least 5% by weight, at least 10% by weight, at least 20% by weight, at least 30% by weight, at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 99% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight, of the total weight of the outer layer. In particular, the outer layer may contain 70-99% by weight, preferably 80-97% by weight, more preferably 85-95% by weight, and especially preferably 88-92% by weight, of the total weight of the outer layer, of the ungrafted polyolefin.

[0067] The further outer layer may contain at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 99% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight, of the total weight of the further outer layer.

[0068] Preferably, the inner layer is specified to contain polyolefin grafted with a silane compound in an amount of at least 1% by weight, at least 10% by weight, at least 20% by weight, at least 30% by weight, at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, or at least 90% by weight, preferably at least 10% by weight, relative to the total weight of the inner layer. In particular, the inner layer may contain polyolefin grafted with a silane compound in an amount of 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight, and especially preferably 8 to 12% by weight, relative to the total weight of the inner layer.

[0069] The inner layer may contain ungrafted polyolefins in addition to polyolefins grafted with silane compounds. The inner layer can contain ungrafted polyolefins in various amounts.

[0070] Preferably, the inner layer contains at least 5% by weight, at least 10% by weight, at least 20% by weight, at least 30% by weight, at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 99% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight, of the total weight of the inner layer. In particular, the inner layer may contain 70-99% by weight, preferably 80-97% by weight, more preferably 85-95% by weight, and especially preferably 88-92% by weight, of the total weight of the inner layer, of the ungrafted polyolefin.

[0071] The further inner layer may contain at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 99% by weight, preferably at least 80% by weight, and more preferably at least 90% by weight, of the total weight of the further inner layer.

[0072] Furthermore, silane-grafted and ungrafted polyolefins may be independently specified to consist 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. In particular, silane-grafted and ungrafted polyolefins may be independently selected from the group consisting of polyethylene, crosslinked polyethylene, heat-resistant polyethylene, polypropylene, polyisobutylene, polybutylene, polymethylpentene, polyalphaolefin, and mixtures thereof.

[0073] Examples of cross-linked polyethylene include PE-Xa, PE-Xb, and PE-Xc. Polyethylene with enhanced heat resistance may also be referred to as PERT.

[0074] When using polyethylene as the polyolefin, it is preferable to use medium-density polyethylene. Medium-density polyethylene may be referred to as MDPE. Advantageously, the medium-density polyethylene has a density of 0.92 g / cm 3 to 0.94 g / cm 3 , more preferably 0.93 g / cm 3 to 0.94 g / cm 3 . Conveniently, the medium-density polyethylene has a melting point of 125 °C to 128 °C. Medium-density polyethylene can be used for both grafted polyethylene and non-grafted polyethylene. When using grafted or non-grafted polyethylene for the outer layer and / or the inner layer, it is preferable to use medium-density polyethylene or grafted medium-density polyethylene. When using grafted or non-grafted polyethylene for a further outer layer and / or a further inner layer, it is preferable to use medium-density polyethylene or grafted medium-density polyethylene. Medium-density polyethylene has the advantage of assisting in the processing of the composite pipe, particularly flexibility and bonding, and thus the laying of the corresponding composite pipe.

[0075] The above polyolefin, particularly polyethylene, has the advantage that its grafting with a silane compound such as vinyltrimethoxysilane is known to those skilled in the art. Thereby, the grafted polyolefin can be produced by a simple and basically known method. The grafting can be carried out, for example, as schematically shown below.

Chemical formula

[0076] Grafting and crosslinking of vinylsilanes are known to those skilled in the art and are described, for example, in “Polyethylene Cross-linking by Two-step Silane Method: A Review”, Iranian Polymer Journal, 18 (2), 2009, pp. 103-128.

[0077] The outer layer and / or any further outer layer may further contain additional substances commonly used in polyolefins, such as antioxidants, pigments, fillers, reinforcing agents, or processing aids. The same applies to the inner layer and / or any further inner layer.

[0078] Examples of fillers include glass fibers, glass beads, calcium carbonate, talc, carbon fibers, natural fibers, polymer beads, and / or carbon black.

[0079] According to one embodiment, the outer layer contains less than 5% by weight, preferably 3% by weight or less, and more preferably 2% by weight or less, of the total weight of the outer layer as filler. According to another embodiment, the inner layer contains less than 5% by weight, preferably 3% by weight or less, and more preferably 2% by weight or less, of the total weight of the inner layer as filler. According to a preferred embodiment, the outer layer and / or inner layer are substantially filler-free. If the composite tube comprises an outer layer and an inner layer, the outer layer and inner layer are particularly preferably substantially filler-free. The same applies to any further inner and / or outer layers.

[0080] Advantageously, the silane compound may be specified to contain 1 to 30 carbon atoms, preferably 2 to 20 carbon atoms, and particularly preferably 2 to 10 carbon atoms. Conveniently, the silane compound has carbon-carbon double and / or triple bonds, preferably carbon-carbon double bonds. Carbon-carbon double and / or triple bonds can be used to graft the silane compound onto the polyolefin as described above.

[0081] The silane compound may have further groups, such as alkylene groups, amine groups, ether groups, thioether groups, hydroxyl groups, epoxy groups, carbamate groups, carbonyl groups, and / or alkyl groups.

[0082] Preferably, the silane compound has 1 to 30 carbon atoms, more preferably 2 to 20, and particularly preferably 2 to 10 carbon atoms, and at least one functional group selected from the group consisting of propargyl, vinyl, acrylic, methacrylic, -OCH3, and -OCH2CH3, and more preferably vinyl, acrylic, methacrylic, -OCH3, and -OCH2CH3.

[0083] Conveniently, silane compounds have the general structural formula (I). (R 2 ) 4-m-o Si(R 3 ) o ((CH2) n R 1 ) m (I) During the ceremony, m is either 1 or 2. o is 0, 1, or 2. Each n is an integer between 0 and 10, independently of the others. Each R 1 These independently represent propargyl, vinyl, -OC(=O)-C(=CH2)H (acryloyloxy), -OC(=O)-C(=CH2)CH3 (methacryloyloxy), and especially vinyl, -OC(=O)-C(=CH2)H (acryloyloxy), -OC(=O)-C(=CH2)CH3 (methacryloyloxy), Each R 2 R independently represents methoxy, ethoxy, isopropoxy, n-propoxy, n-butoxy, sec-butoxy, or isobutoxy, or two or three R 2 However, each is independent of the others C 1~5 They are bonded together by alkylene groups. Each R 3 C is independent of each other. 1~4This represents alkyl, especially methyl or ethyl.

[0084] Preferably, in structural formula (I), R 1 n is 0 only if it represents vinyl.

[0085] More preferably, the silane compound may be specified to have structural formula (II). R 4 -(CH2) p -Si(OR 5 )3(II) During the ceremony, R 4 This represents HC≡C-, H2C=CH-, H2C=CH-C(O)-O-(acryloyloxy) or H2C=C(CH3)-C(O)-O-(methacryloyloxy), and especially H2C=CH-, H2C=CH-C(O)-O-(acryloyloxy) or H2C=C(CH3)-C(O)-O-(methacryloyloxy), Each R 5 These are -CH3, -C2H5, -C3H7, -C4H9, or -C5H, independently of each other. 11 It represents either two or three R's 5 However, each is independent of the others C 1~5 They are bonded together by alkylene groups. p is an integer between 0 and 10.

[0086] Particularly preferred, R 4 This represents H2C=CH-, and each R 5 These represent -CH3 or -CH2CH3 independently of each other, and p is 0. 4 When HC≡C- represents the relationship between HC and C-, p is preferably an integer between 1 and 10.

[0087] More preferably, the silane compound is vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrialkoxysilane used in esterification with different alcohols, propargyltrimethoxysilane, propargyltriethoxysilane, propargyltrialkoxysilane used in esterification with different alcohols, 4-pentenyltrimethoxysilane, 4-pentenyltriethoxysilane, 10-undecenyltrimethoxysilane, 10-undecenyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltriethoxysilane, 2-acryloyloxyethyltrimethoxysilane, 2-acryloyloxyethyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 2-methacryloyl The silane compound may be specified to be selected from the group consisting of oxyethyltriethoxysilane and mixtures thereof, preferably vinyltrimethoxysilane, vinyltriethoxysilane, vinyltrialkoxysilane in which a different alcohol is used for esterification, 4-pentenyltrimethoxysilane, 4-pentenyltriethoxysilane, 10-undecenyltrimethoxysilane, 10-undecenyltriethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltriethoxysilane, 2-acryloyloxyethyltrimethoxysilane, 2-acryloyloxyethyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 2-methacryloyloxyethyltrimethoxysilane, 2-methacryloyloxyethyltriethoxysilane and mixtures thereof. Particularly preferred is that the silane compound is vinyltrimethoxysilane, vinyltriethoxysilane, or a mixture thereof.

[0088] <Examples> Conventional PE (Sclair® 74B, purchased from Nova Chemicals) was reactively grafted with 2 m% vinyltrimethoxysilane (Silquest® A-171, purchased from Momentive) and 0.05 m% 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (purchased from VWR) in a twin-screw extruder at a temperature profile of 150°C to 220°C. After the product was discharged from the nozzle, it was cooled and pelletized.

[0089] Polyethylene grafted with vinyltrimethoxysilane (hereinafter referred to as "PE-gSil"), manufactured according to the above instructions, was pressed onto a steel plate with a plate press at a temperature of 250°C and a pressure of 100 bar for 2 minutes. The peeling force of the polyethylene from the steel plate was determined to be greater than 50 N / cm at 25°C and a peeling rate of 50 mm / min, in accordance with DIN EN ISO 11339:2022-05.

[0090] For comparison, ungrafted polyethylene (Sclair 74B) was pressed against a steel plate at a temperature of 250°C and a pressure of 100 bar for 2 minutes. The peeling force of the polyethylene from the steel plate was determined to be 0 N / cm at 25°C and a peeling rate of 50 mm / min, in accordance with DIN EN ISO 11339:2022-05.

[0091] Test specimens prepared according to the method described above were aged in water at 105°C. Simultaneously, samples using a conventional high-performance PE-gMAH-based fixative (Admer NE072 from Mitsui Chemicals, Inc.) were also aged. For comparison, the peel force was measured over the aging period. The PE-gMAH-based sample exhibited a peel force of less than 2.5 N / cm after 3000 hours at 25°C and a peeling rate of 50 mm / min according to DIN EN ISO 11339:2022-05, while the PE-gSil sample prepared according to the procedure described above showed a peel force of more than 40 N / cm at 25°C and a peeling rate of 50 mm / min according to DIN EN ISO 11339:2022-05. No peeling was observed in the PE-gSil-based sample.

[0092] The difference in peel force retention between PE-gMAH-based and PE-gSil-based fixing agent systems applies directly to composite tube samples fabricated by extrusion.

[0093] The present invention will be described below with reference to the drawings, based on the examples provided. [Brief explanation of the drawing]

[0094] [Figure 1] This is a diagram showing the first embodiment of the composite pipe. [Figure 2] This figure shows a second embodiment of the composite pipe. [Figure 3] This figure shows a third embodiment of the composite pipe. [Figure 4] This figure shows a fourth embodiment of the composite pipe. [Figure 5] This figure shows an unpressed joint for connecting the composite pipes shown in Figure 2. [Figure 6] Figure 5 shows the composite pipe and the joint in a compressed state.

[0095] In the following description of various embodiments of the present invention, even if the dimensions or shapes of the parts and elements may differ in the various embodiments, parts and elements having the same function and mode of operation are given the same reference numerals.

[0096] Figure 1 shows a composite tube 1 for guiding and directing a fluid, preferably water in the form of drinking water or heated water. The composite tube 1 comprises a stabilizing layer 2 having an outer surface 3 and an outer layer 4.

[0097] Here, the outer layer contains a polyolefin grafted with at least one silane compound.

[0098] According to the present invention, the outer layer 4 is bonded to the outer surface 3 of the stabilizing layer 2 by at least one silane compound of the grafted polyolefin. As a result, the stabilizing layer 2 and the outer layer 4 form a hydrostabile bond that is stronger than when an MAH fixing agent is used, preventing the layers from being eroded by moisture penetration and preventing damage to the composite pipe. For the presumed mechanism, please refer to the general explanation.

[0099] Figure 2 shows another composite tube 11 comprising a stable layer 12 having an outer surface 13 and an outer layer 14. Furthermore, an inner layer 16 is provided. The inner layer 16 contains a polyolefin grafted with at least one silane compound, and the inner layer 16 is bonded to the inner surface 15 of the stable layer 12 by at least one silane compound of the grafted polyolefin. No crosslinking catalyst was used during the bonding of the inner layer 16 and the stable layer 12.

[0100] Therefore, the inner layer 16 is bonded to the stable layer 12 via the inner surface 15 with higher hydrolysis stability than when an MAH fixing agent is used. For an explanation of this bond, please refer to the general section of this specification.

[0101] Figure 3 shows another embodiment of the composite tube 21 for guiding and directing fluid. In this embodiment, a stabilizing layer 22 and an inner layer 26 are provided. The outer layer, as in the embodiments shown in Figures 1 and 2, is not present here.

[0102] The inner layer 26 contains a polyolefin grafted with at least one silane compound. Furthermore, the inner layer 26 is bonded to the inner surface 25 of the stable layer 22 by at least one silane compound of the grafted polyolefin. No crosslinking catalyst was used during the bonding of the inner layer 26 and the stable layer 22.

[0103] Therefore, the inner layer 26 is bonded to the stable layer 22 via the inner surface 25 with higher hydrolysis stability than when an MAH fixing agent is used. For an explanation of this bond, please refer to the general section of this specification.

[0104] Figure 4 shows another composite tube 31 comprising a stable layer 32 having an outer surface 33 and an outer layer 34. Here, the outer layer contains a polyolefin grafted with at least one silane compound. Furthermore, the composite tube 31 comprises a further outer polyolefin layer 37 bonded to the outer layer 34 via its outer surface 38.

[0105] According to the present invention, the outer layer 34 is bonded to the outer surface 33 of the stabilizing layer 32 by at least one silane compound of the grafted polyolefin. As a result, the stabilizing layer 32 and the outer layer 34 form a water-resistant bond that is stronger than when an MAH fixing agent is used, so that the layers are not eroded by moisture penetration and the composite pipe is not damaged. For the presumed mechanism, please refer to the general description. A further outer polyolefin layer 37 is bonded to the outer layer 34 by a mechanism known to those skilled in the art.

[0106] In the embodiments shown in Figures 1 to 4, the stabilizing layers 2, 12, 22, and 32 contain metallic materials, and in particular, the stabilizing layers are made of metallic materials. In this case, the use of copper and aluminum is preferred.

[0107] The outer layers 4, 14, 34 and / or inner layers 16, 26 contain in some proportion polyolefins grafted with silane compounds, preferably polyethylene grafted with vinyltrimethoxysilane. Theoretically, this proportion can be 100% by weight. However, a lower proportion of 10% by weight is preferred. In this case, the remaining proportion can be ungrafted polyolefins, preferably polyethylene.

[0108] To characterize the outer surfaces 3, 13, 33 and / or inner surfaces 15, 25 of the stable layers 2, 12, 22, 32, they have a static initial contact angle of water of 110° or less after equilibration for 3 minutes, as determined in accordance with DIN EN ISO 19403-2:2020-04.

[0109] Furthermore, the outer layers 4, 14, and 34 are attached to the outer surfaces 3, 13, and 33 of the stabilizing layers 2, 12, and 32, and / or the inner layers 16 and 26 are attached to the inner surfaces 15 and 25 of the stabilizing layers 12 and 22, with a peeling force of at least 15 N / cm, determined by 25°C and a peeling rate of 50 mm / min in accordance with DIN EN ISO 11339:2022-05.

[0110] Figures 5 and 6 show a system for forming a pipeline connection, comprising a composite pipe 11 as shown in Figure 4 and a fitting 40 for an external seal.

[0111] The joint 40 comprises a base 44 and a contact element 45 formed circumferentially on the base 44 and projecting inward. Furthermore, a press sleeve 41 is provided that connects to the base 44 and forms an outer contour 42, and the press sleeve 41 has a chamber 43 that faces inward toward the pipe 11 to be housed. Inside the chamber 43 is a plastic clamp ring 46 having a plurality of clamp elements 47 aligned in the opposite direction to the withdrawal direction of the inserted pipe 31. In addition, a seal element 48 is located inside the chamber 43 adjacent to the contact element 45.

[0112] Since the press sleeve 41 is integrally bonded to the base body 44, the press portion in the form of the press sleeve 41 and the base body 44 can be advantageously manufactured as a single unit.

[0113] The positioning of the pipe 31 against pull-out and / or excessively high internal pressure is achieved by a clamp ring 46, which is formed as a plastic clamp ring and positioned on a metal blade as a clamping element 47. The plastic clamp ring 46 further has circumferentially extending slits, which make the entire clamp ring 46 flexible, facilitating its attachment to the fitting 40 within the press sleeve 41.

[0114] The clamping elements 47 are configured as blades in the form of wire elements and are inserted into notches provided therefor. This causes the clamping elements 47 to be morphologically fixed to the plastic of the clamping ring 46. The clamping elements 47 may be manufactured in various ways, for example, as cast or stamped parts. The number of clamping elements 47 is six in this case, but can be determined according to the requirements or dimensions of the clamping ring 47.

[0115] The clamp element 47 is further positioned in the distal region of the chamber 43 opposite the contact element 45, and as shown in Figure 6, the clamp element 47 absorbs the pull-out force by deforming the pipe 31 at a specific point, while being supported by the wall of the distal outer corner region 41a of the press sleeve 41. This ensures a direct flow of force from the pipe 31 through the press sleeve 41 to the joint 40. After pressing, the clamp ring 46 has only a support function and contributes little to no to preventing pull-out.

[0116] The pressing process is evident from comparing Figures 5 and 6. A press jaw half (not shown) moves radially inward, and as the press jaw half contacts the press sleeve 41, the press sleeve 41 deforms radially inward. This causes, on the one hand, the clamp ring 46 to deform, and the clamp element 47 to be pushed inward into the material of the pipe 31, thereby securing the pipe 31 to the fitting 40. On the other hand, as the press sleeve 41 deforms, the seal 48 also deforms radially inward, and the seal 48 forms a seal between the pipe 31 and the press sleeve 41.

[0117] As described above, a key advantage of composite tube 31, as well as the other embodiments of composite tubes 1, 11, and 21 described, is that the outer layer 34 adheres to the outer surface 33 of the stabilizing layer 32 by at least one silane compound of the grafted polyolefin, thereby creating a bond between the stabilizing layer 32 and the outer layer 34 that is more hydrolysis-resistant than when an MAH fixing agent is used. Preferably, no crosslinking-promoting catalyst is used during the bonding of the stabilizing layer and the outer layer.

[0118] As a result, as shown in Figure 6, the composite pipe 31 and the joint 40 are joined by being pressed only from the outside, allowing the end face 39 of the composite pipe 131 to come into unprotected contact with a medium such as water introduced into the pipe 31 and joint 40, thus preventing damage to layers 32, 34, and 37 due to hydrolysis. Therefore, with the above configuration of the composite pipe 31, pressing on the inside of the pipe using a conventional support may become unnecessary.

[0119] In this case, there is a particular advantage in that the presence of a support in the cross-section of the joint between the composite pipe 31 and the fitting 40 is avoided. This reduces pressure loss in the pipeline assembly.

Claims

1. A composite tube (1, 11, 31) for guiding and directing fluid, - A stable layer (2, 12, 32) having an outer surface (3, 13, 33), - An outer layer (4, 14, 34) containing a polyolefin grafted with at least one silane compound and In a composite pipe (1, 11, 31) equipped with, - The outer layer (4, 14, 34) is bonded to the outer surface (3, 13, 33) of the grafted polyolefin by at least one silane compound. A composite pipe (1, 11, 31) characterized by the above.

2. - An inner layer (16) containing a polyolefin grafted with at least one silane compound is provided. - The inner layer (16) is bonded to the inner surface (15) of the stabilizing layer (12) by at least one silane compound of the grafted polyolefin. The composite pipe (11) according to claim 1, characterized in that

3. A composite tube (21) for guiding and directing fluid, - Stabilizing layer (22), - An inner layer (26) containing a polyolefin grafted with at least one silane compound and In a composite pipe (21) equipped with, - The inner layer (26) is bonded to the inner surface (25) of the stabilizing layer (22) by at least one silane compound of the grafted polyolefin. A composite pipe (21) characterized by the above.

4. The outer layer (4, 14, 34) is bonded to the outer surface (3, 13, 33) of the grafted polyolefin by at least one silane compound without the use of a crosslinking-promoting catalyst, and / or The inner layers (16, 26) are bonded to the inner surfaces (15, 25) of the grafted polyolefin by at least one silane compound, without the use of a crosslinking-promoting catalyst. A composite pipe (1, 11, 21, 31) according to any one of claims 1 to 3, characterized in that

5. The composite tube (1, 11, 21, 31) according to any one of claims 1 to 4, characterized in that the stabilizing layer (2, 12, 22, 32) contains a metallic material, and is particularly made of a metallic material.

6. The composite tube (1, 11, 21, 31) according to any one of claims 1 to 5, characterized in that the stabilizing layer (2, 12, 22, 32) is made of at least a portion of a nonmetallic material.

7. The composite tube (1, 11, 21, 31) according to any one of claims 1 to 6, characterized in that the outer surface (3, 13, 33) of the stabilizing layer (2, 12, 32) and / or the inner surface (15, 25) of the stabilizing layer (12, 22) have a static initial contact angle of 110° or less, preferably 100° or less, and more preferably 90° or less, of water after equilibration for 3 minutes, as determined in particular in accordance with DIN EN ISO 19403-2:2020-04.

8. The composite tube (1, 11, 21, 31) according to any one of claims 1 to 7, characterized in that the outer layer (4, 14, 34) is attached to the outer surface (3, 13, 33) of the stabilizing layer (2, 12, 32), and / or the inner layer (16, 26) is attached to the inner surface (15, 25) of the stabilizing layer (12, 22), with a peeling force of at least 15 N / cm, preferably at least 30 N / cm, and more preferably at least 50 N / cm, determined in accordance with DIN EN ISO 11339:2022-05 at 25°C and a peeling rate of 50 mm / min.

9. The composite tube (1, 11, 21, 31) according to any one of claims 1 to 8, characterized in that it is provided with 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.

10. A method for manufacturing a composite tube (1, 11, 31) according to any one of claims 1 to 9, - Prepare a stable layer (2, 12, 32) having an outer surface (3, 13, 33), - An outer layer (4, 14, 34) containing a polyolefin grafted with at least a silane compound is applied to the outer surface (3, 13, 33) of the stabilizing layer (2, 12, 32). method.

11. The method according to claim 10, wherein the outer layers (4, 14, 34) are attached to the stabilizing layers (2, 12, 32) by tube extrusion.

12. - The method according to claim 10 or 11, wherein an inner layer (16) containing a polyolefin grafted with at least a silane compound is applied to the inner surface (15) of the stabilizing layer (12).

13. A method for manufacturing a composite tube (21) according to any one of claims 3 to 9, - Prepare a stable layer (22) having an inner surface (25), - An inner layer (26) containing a polyolefin grafted with at least a silane compound is applied to the inner surface (25) of the stabilizing layer (22). method.

14. The stabilizing layers (2, 12, 22, 32) are heated, in particular by induction heating, before and / or after the application of the inner layers (16, 26) and / or the outer layers (4, 14, 34), and / or The inner layers (16, 26) and / or the outer layers (4, 14, 34) are coated without the use of a crosslinking-promoting catalyst. The method according to any one of claims 10 to 13.

15. A system for forming pipeline connections, - A composite pipe (1, 11, 21, 31) according to any one of claims 1 to 9, - Fitting (40) for the outer seal and A system that includes these features.

16. Use of the composite pipe (1, 11, 21, 31) according to any one of claims 1 to 9, particularly in a water conduit assembly for drinking water or hot water.

17. The use of polyolefins grafted with silane compounds as a fixative for bonding polyolefin-containing layers to stable layers, particularly metal layers.

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