Non-metallic tube for improved tube bending

Abstract

The present invention provides a plastic pipe for use in a piping system and manually bent 90 DEG, the pipe comprising: a) a first polyethylene layer comprising high temperature resistant polyethylene (PE-RT) forming the longitudinal axis of the pipe; the PE-RT layer comprises between 5% and 60% by weight of an inorganic filler having an average particle size of a particle size (D50) of from 0.5 [mu] m to 40 [mu] m.

Description

Technical Field

[0001] The present invention relates to a tube having a certain height, such as a multi-layer tube and a method for manufacturing the same. Specifically, the present invention relates to a tube, such as a multi-layer tube to be used for transporting hot or cold fluids, for example, in heating, cooling or water supply systems. Background Art

[0002] The supply of water (which may be drinking water, hot water or water for central heating or HVAC (heating, ventilation and air conditioning) purposes) in buildings is delivered in tubes. For small buildings and offices, these tubes typically have a diameter of about 20 mm, and in larger buildings, such small tubes are present at the end of the distribution chain. Whether larger or smaller in size, such tubes are typically installed manually during the building construction process or retrofitted into existing buildings. Therefore, it is more efficient during the construction process if the tubes can be provided in long lengths and then bent to traverse a specific route within the building. Historically, metal tubes, such as tubes made of metal or steel, have been used, and these tubes can be manually bent and retain their shape. More recently, due to various reasons, including cost and the environment, there has been a shift to plastic tubes. Different from metal tubes, such tubes can easily be made in very long lengths and can be transported on site in large rolls. Such tubes have resilience, i.e., they return to their initial form after being bent, and thus cross a given path in a building by adding specific joint parts. This is relatively inefficient. The tubes can alternatively be permanently bent by heating and cooling the tubes. This is inconvenient on site and may be non-renewable, usually requiring temperatures in excess of 200 °C. This is one of the reasons for producing plastic tubes with an aluminum layer. Such tubes can be bent without elastic recovery of the shape. However, such tubes may be difficult to recycle because they are plastic / metal composites.

[0003] Therefore, there is a need for a tube comprising a plastic material that can be manually bent without significant elastic recovery.

[0004] Multi-layer plastic tubes have widely replaced single-layer metal or plastic tubes, which were previously commonly used in the construction industry. By combining the advantageous properties of different layers, such as specific rigidity, corrosion resistance and / or effective manufacturability, they can outperform single-layer tubes.

[0005] Multi-layer tubes have been developed that include a barrier layer adapted to block the passage of fluids, such as air or moisture. Commonly used barrier layers include aluminum or EVOH (ethylene-vinyl alcohol copolymer). The barrier layer can protect the fluid transported in the tube from the diffusion of other fluids, such as contaminants in the ground, into the tube.

[0006] A tube having high strength, heat resistance, and exhibiting additional barrier properties would seem desirable. However, when attempting to manufacture a multi-layer tube exhibiting both enhanced and barrier properties, for example, by combining the aforementioned tube including a reinforcing layer with an additional barrier layer, problems are encountered with the interlayer bonding and mechanical properties of the tube deteriorating.

[0007] For example, it is known that vapor diffusion through the multiple layers of a multi-layer tube causes physical defects, which can lead to problems with tube stability and lifespan. Two types of physical defects that have been identified are blistering and bulging. Blistering is caused by small air bubbles that appear within one or more of these individual layers of the multi-layer tube due to vapor diffusion of the liquid that the tube is designed to transport. Bulging is a similar but more severe condition to blistering, as the air bubbles generated due to transporting the liquid through the multi-layer tube are generally larger than those generated during the blistering process. Another problem is that the larger bubbles tend to appear at the interface between two layers in the multi-layer tube, which can lead to layer rupture or separation. For example, Rehau's Technical Information Sheet No. 850624 released in January 2013 acknowledges that "blistering may occur during operation on the tube surface". The two problems of vapor diffusion through the multiple layers of a multi-layer tube can create defects within the tube itself, which can lead to catastrophic failure, especially when the tube is used at a certain pressure and / or temperature.

[0008] Previously, it has been found that nanoclays can be used in the food packaging industry. An emerging area in this field is polymer nanocomposite (PNC) technology, which involves combining different chemicals and nano-additives into polymers to improve their inherent properties or add required functionality. Since these nanoparticles can interact with food components during processing, storage, or distribution and can migrate into the food, PNC-based packaging materials need to understand and comprehend their potential impact on human health and the environment. In recent years, there has been a significant increase in the attention given to the migration and cytotoxicity analysis of PNCs. It is known that clay-containing PNCs account for 50% of all nano-fillers, where the nanoclays are natural or synthetic.

[0009] CN112066095 discloses a high-rigidity heat-resistant high-density polyethylene tube, including a main pipe body and a reinforcing pipe. The production raw material of the main pipe body is a composite heat-resistant polyethylene (PE-RT) material, and the tube of the polypropylene (PP) corrugated pipe in the reinforcing pipe is "PPR" or "PPB". The use of inorganic fillers is disclosed. If the inorganic fillers are talc powder and mica, their size is disclosed as 1000 - 4000 mesh (25μm to 5μm), but it is not disclosed whether the material remains at that mesh size or passes through that mesh size. The rigid tube is used for large-diameter wastewater pipes.

[0010] WO 2021165290A1 discloses a multi-layer flexible packaging material, comprising a paper layer, an aluminum layer, a nanoclay barrier coating, and a sealant layer applied to the surface of the nanoclay barrier coating, representing the inner surface of the multi-layer flexible packaging material. The multi-layer barrier material is free of polyolefin layers, such as polyethylene (PE), polyethylene terephthalate (PET), or polypropylene (PP) layers.

[0011] US2017029196A1 discloses a heat-sealable food packaging film, a method for preparing the same, and a food packaging comprising the heat-sealable food packaging film. The heat-sealable food packaging film comprises a humidity-dependent permeable film whose moisture transmission rate increases as the relative humidity (RH) increases. The outer coating comprises a coating material on at least one surface of the humidity-dependent permeable film. The coating material is selected from nanoclays dispersed in a polyvinylidene chloride (PVdC) polymer or a stretchable urethane polymer, a stretchable acrylic polymer, or a combination of a stretchable urethane polymer and a stretchable acrylic polymer.

[0012] DE10120620A1 discloses a multi-layer polyamide plastic pipe for conveying a fluid medium in heating and sanitary equipment, which comprises at least one layer configured as a multi-material layer composed of a polymer with incorporated nanoclay processed as a filler element. A number of adhesive layers need to be present between the individual layers, which results in an increased risk of blistering.

[0013] KR20110052265A discloses a fuel injection pipe using a nanocomposite to significantly reduce the emissions of fuel evaporation gas generated when using variable fuels. The fuel injection pipe using the nanocomposite comprises the nanocomposite. The nanocomposite is formed by mixing 97% - 99.7% of an engineering plastic and 0.3% - 3% of nanoclay by extrusion or three-dimensional blow molding. The engineering plastic is polyamide.

[0014] Therefore, there has been no consideration of using nanoclay in combination with high-density or ultra-high molecular weight polyethylene for transporting hot or cold fluids in heating, cooling, or water supply systems to prevent problems caused by blistering or bulging in multi-layer pipes. Therefore, it would be advantageous to overcome the problems of the prior art by incorporating a nanoclay material into one of the multiple layers of a multi-layer pipe to reduce gas transmission through the layers.

[0015] However, although multi-layer pipes offer multiple benefits, as described above, they are particularly prone to springback recovery when bent, and thus there is a need for a multi-layer pipe made of a plastic material that can be manually bent without significant springback recovery. Summary of the Invention

[0016] In the terminology of the present application, a pipe made of plastic material is a pipe in which there is no continuous phase layer that is not plastic. Thus, such a pipe may have additional components, but the layers of these additional components do not provide a continuous phase, meaning it is not possible to reach from one side of the pipe to the other without encountering plastic.

[0017] The present invention provides:

[0018] A plastic pipe for use in a pipe system, the pipe comprising:

[0019] At least one PE-RT layer, the at least one PE-RT layer comprising from 30% to 95% PE-RT and inorganic filler.

[0020] The present invention is suitable for use in pipe systems, i.e., systems of pipes, tanks, fittings, and other devices required for water supply, heating, and sanitation in buildings. The pipes related to the present invention are mainly used for water supply, especially for both hot and potable water as well as for central heating water.

[0021] The present invention as claimed is set forth in the appended claims.

[0022] The present invention provides a plastic pipe for use in a pipe system and manually bendable at 90°, the pipe comprising:

[0023] a) A first polyethylene layer, which comprises high temperature resistant polyethylene (PE-RT) forming the longitudinal axis of the pipe;

[0024] The PE-RT layer comprises an inorganic filler between 5% and 60% by weight, the inorganic filler having an average particle size (D 50 ) from 0.5 μm to 40 μm.

[0025] The plastic pipe of the present invention is suitable for being manually bent at 90° and, in doing so, maintaining structural integrity and suitability for pipe system applications. In fact, this means being able to withstand a difficult operating pressure of at least 70 kPa up to 700 kPa. This can be quantified as follows: The pipe according to the present invention can have a burst pressure of at least 2 MPa, preferably at least 6 MPa, or preferably at least 7 MPa after being manually bent at 90° (as described herein). The burst test is carried out at room temperature according to the ASTM D1599-18 standard.

[0026] This can be used to distinguish the plastic pipe according to the present invention from plastic pipes that can simply be bent but cannot maintain their structural integrity. The plastic pipe according to the present invention can be bent at ambient temperature (taking 20 °C) and maintain its structural integrity. The pipe according to the present invention has the advantage that, after having been bent as such, it not only maintains its structural integrity, but also, when unconstrained, it can still maintain the bent shape. As described in the following method, this can be quantified by having a relaxation of less than 5° after bending 90° twice. This distinguishes the present invention from other by-products that require heating and cooling, such as above 200 °C, more typically above 400 °C, before they can be effectively bent manually, and / or bending at ambient temperature provides extensive microcracks (usually evidenced by white coloring), which reduces the structural integrity of the pipe and / or the pipe provides a relaxation of more than 5° after bending 90° for 24 hours, preferably after two weeks.

[0027] Preferred inorganic fillers for use in the present invention are talc - Mg3Si4O 10 (OH)2 and calcium carbonate - CaCO3. Both of these fillers reduce the springback recovery of the bent pipe, such that the bend can be maintained, which is useful, for example, for subsequent installation of the pipe in a pipe system. Inorganic fillers are preferred because they do not have resilience themselves, and inorganic fillers are preferred because they do not mix with the polymer in which they are present, such as when preparing a masterbatch. Inorganic fillers having a relatively high surface area are preferred, although nanoscale materials do not seem to be very effective in altering the elastic recovery.

[0028] The pipe according to the present invention may preferably further comprise, b) a ultra-high molecular weight polyethylene (UHMWPE) layer disposed around the first PE-RT layer.

[0029] This provides a tougher pipe, such as being more impermeable and having low moisture permeability.

[0030] The pipe according to the present invention may further comprise c) a ultra-high molecular weight polyethylene (UHMWPE) layer disposed within the first PE-RT layer. This provides a shield against the supply of water from any soluble components in the PE-RT layer and also reduces the gas permeability.

[0031] The pipe according to the present invention may further comprise d) a second PE-RT layer, and

[0032] d1) disposed outside the previously claimed layer b) or d2) disposed inside the previously claimed layer c). This enables each PE-RT layer to be customized for optimal properties. For example, one layer can be customized to provide low gas permeability, while another layer can be customized to retain its shape after bending. Mixing additives into a single layer is not necessarily synergistic, whereas providing separate layers with separate functions, such as to give a total layer thickness equal to the total layer thickness of a single thicker layer, can give a higher efficiency of combination in terms of these two properties, for example.

[0033] In the present invention, at least one layer further comprises a nanoclay material for reducing gas transmission through the layer. This is advantageous because gas transmission (such as in the form of water) into a layer containing inorganic fillers can cause hydration or dissolution of some of the fillers, as well as reduce the life of the pipe and / or because the filler components migrate into the water supply.

[0034] In the present invention, at least one layer that does not include inorganic fillers includes a nanoclay material for reducing gas transmission through the plurality of layers. This separation of the plurality of layers as described above enables a generally significant improvement in properties and simplifies the process.

[0035] In the present invention, the innermost PE-RT layer a) can be surrounded by a UHMWPE layer b), and the UHMWPE layer b) is in turn surrounded by a PE-RT d1) that includes a nanoclay material for reducing gas transmission through the layer.

[0036] In this structure, the nanoclay can be present in the UHMWPE layer c). This can, for example, enable both PE-RT layers to include fillers.

[0037] In the present invention, the amount of nanoclay present in a particular layer can be at most 10 wt.% (weight percentage) of the corresponding layer in which it is located. This level (such as a level between 2% and 10%) provides an effective reduction in gas permeability. A critical high level can be disadvantageous because the components may leach out of the layer, for example, into the water supply.

[0038] In the present invention, the thickness of the first PE-RT layer a) is in the range of 1.3 mm to 7.2 mm. This provides a suitable range such that manual bending is practical.

[0039] In the present invention, the thickness of the second PE-RT layer b) is in the range of 0.1 mm to 0.9 mm. Especially when this layer is disposed on the outer side of the pipe as the second layer, the additional volume of the outer layer enables this layer to be made relatively thin and still be effective.

[0040] In the present invention, the thickness of the UHMWPE layer ranges from 0.1 mm to 0.7 mm. A thick layer is disadvantageous because UHMWPE is highly resilient and not conducive to tube bending, and a thinner layer is less effective in terms of mechanical strength and reducing water transmission.

[0041] In the present invention, the UHMWPE layer is formed from UHMWPE tapes, and the layer optionally comprises two layers of tapes, one layer on top of the other. This is more effective than coextrusion, as the difference in melting points between UHMWPE and PE-RT means that coextrusion can be problematic.

[0042] In the present invention, when using UHMWPE tapes, the two tape layers have an overlap angle between 40° and 70° therebetween, which provides an effective seal and minimizes the resilience of the layer in its role of resisting the retention of a bent tube shape.

[0043] The present invention may further comprise an adhesive layer disposed between the first PE-RT layer and the UHMWPE layer, and / or an adhesive layer disposed between the second PE-RT layer and the UHMWPE layer.

[0044] In the present invention, the tube is preferably made of metallic aluminum or copper. The present invention is particularly beneficial as it allows the removal of such conventional metals to enable tube bending, while retaining the bends made, for installation such as in a pipe system. Plastic tubes without metallic elements are also recycled more effectively, and the possibility of such metal corrosion and the entry of such metals into the water supply are avoided.

[0045] The tube according to the present invention may comprise a layer consisting of said components, however, this layer or these layers optionally comprise less than 5% by weight of minor additives. Such additives include plasticizers, flame retardant additives, antioxidants, colorants, UV stabilizers. Preferably, all such components are present in amounts not greater than 2% by weight of such components.

[0046] A preferred example of the present invention is a first PE-RT layer on the inside containing an inorganic filler between 5% and 60% by weight, the inorganic filler having an average particle size (D 50 ) ranging from 0.5 μm to 40 μm; a UHMWPE layer; and a second PE-RT layer on the outside containing a nanoclay material. This provides an optimal combination of shape retention upon bending, physical toughness, and reduced gas permeability for tubes used in pipework.

[0047] In another aspect of the present invention, the present invention provides a method of manufacturing a tube as further disclosed herein. The present invention thus also includes a method of manufacturing a multi-layer polymer tube, the method comprising the following steps:

[0048] Melt-extrude a first PE-RT layer a) to form the longitudinal axis of the tube; melt-extrude a UHMWPE layer b) over the first PE-RT layer; and apply a second PE-RT layer d1) over the UHMWPE layer.

[0049] The object of the present invention is to provide a durable multi-layer tube which has good retention on bends but has sufficient resilient flexibility such that a small degree of bending (such as up to 25°) can rebound and recover. When containing nano-clay, the tube 50 of the present invention also provides a sufficient oxygen barrier effect by adopting a nano-clay material for reducing gas transmission through the layers. An important feature of the present invention is the ability of the tube to bend and elastically recover (performing well under a small degree of bending).

[0050] It has been surprisingly found that a multi-layer tube having a layer comprising at least one nano-clay material reduces gas transmission through the multiple layers of the tube. Preventing the diffusion of gas from the air surrounding the tube into the liquid medium, especially at high operating temperatures or high pressures of the fluid medium carried in the tube, is considered beneficial for extending the life of the tube.

[0051] Preferably, the nano-clay is dispersed in at least one of the first PE-RT layer or the second PE-RT layer. It is known that nano-clay materials have excellent oxygen barrier properties to prevent vapor from diffusing through the multiple layers of the multi-layer tube. More preferably, the nano-clay is dispersed in the second (outer) PE-RT layer. The nano-clay-containing outer layer of the multi-layer tube provides an oxygen barrier layer adjacent to the surrounding environment to maximize the reduction of potential water vapor diffusing through the multiple layers of the multi-layer tube, which may otherwise cause blistering or bulging.

[0052] Preferably, the nano-clay is dispersed in the UHMWPE layer. When present in the UHMWPE layer, the water absorption of the nano-clay decreases with an increase in the nano-clay concentration. This improvement is attributed to the reduced water absorbency of the organo-clay composite, resulting in less softening and plasticization of the UHMWPE polymer layer and leading to better wear resistance.

[0053] Preferably, the amount of the nanoclay accounts for at least 0.5 wt.%, preferably 1.0 wt.%, preferably 1.5 wt.%, preferably 2.0 wt.%, preferably 2.5 wt.%, preferably 3.0 wt.%, preferably 3.5 wt.%, preferably 4.0 wt.%, preferably 4.5 wt.%, or preferably 5.0 wt.% of the corresponding layer in which it is located. Preferably, the amount of the nanoclay accounts for at most 5 wt.%, preferably 5.5 wt.%, preferably 6.0 wt.%, preferably 6.5 wt.%, preferably 7.0 wt.%, preferably 7.5 wt.%, preferably 8.0 wt.%, preferably 8.5 wt.%, preferably 9.0 wt.%, preferably 9.5 wt.%, preferably 10.0 wt.%, preferably 10.5 wt.%, preferably 11.0 wt.%, preferably 11.5 wt.%, preferably 12.0 wt.% of the corresponding layer in which it is located. Preferably, the amount of the nanoclay accounts for at most 10 wt.% of the corresponding layer in which it is located. The permeability and diffusivity of water vapor through different layers of the multi-layer tube are significantly reduced by incorporating the nanoclay at a level of at most 10 wt.% of the corresponding layer in which it is located into the polymer matrix.

[0054] Preferably, the nanoclay is montmorillonite, and its chemical formula is (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), which is hydrated sodium calcium aluminum magnesium hydroxide silicate. It is known that nanoclay materials have excellent oxygen barrier properties to prevent vapor diffusion. Incorporating nanoclay into the polymer matrix enhances the mechanical, physical, and barrier properties of the polymer. Montmorillonite, kaolinite, and saponite are examples of nanoclays that have been used as fillers in food systems. Montmorillonite has particularly attracted great attention in the food industry due to its low cost, availability, simple processability, and significant improvement in performance. Preferably, the nanoclay is Na + , which is an unmodified type of nanoclay material

[0055] Surface modification of the nanoclay also provides improved compatibility with the polymer matrix in which it is embedded.

[0056] Preferably, the nanoclay is surface-modified with a quaternary ammonium salt. Preferably, the quaternary ammonium salt is a modified dialkyldimethyl, arylalkyldimethyl, or diaryldimethyl quaternary ammonium salt having the following general formula:

[0057] (CH3)2N + (R)2

[0058] wherein each R group is independently a straight-chain alkyl chain having 8 to 18 carbon atoms, more preferably 12 to 16 carbon atoms, or an aryl group having 6 to 12 carbon atoms, more preferably 6 carbon atoms. Suitable counterions generally include chlorides.

[0059] Preferably, the alkyl chains of the dialkyl or alkyl moieties of the quaternary ammonium salt have equal chain lengths. Preferably, such carbon chain lengths comprise from 16 to 18 carbon atoms. When incorporated into polyethylene, this appears to improve the thermal stability and provide better exfoliation of the clay.

[0060] Preferably, these alkyl chains have hydroxyl end groups in order to improve the compatibility with the polar clay component, potentially providing a shorter mixing time.

[0061] Preferably, the aryl group is benzyl. This appears to improve the thermal stability, such as that required for UHMWPE processing.

[0062] Preferably, the nanoclay is selected from 10A, 15A, 20A, 30B or one or more of 93A. Most preferably, the nanoclay is 20A because it uses a cationic surfactant. 20A results in a reduction of the surface energy of the nanoclay material and helps to enhance the wetting in the polymer matrix. In addition, the presence of aliphatic tails attached to the cationic groups results in an increase in the d-spacing or interlayer spacing of the nanoclay layers, thus improving exfoliation and related physical properties.

[0063] Preferably, the amount of nanoclay present in at least one layer of the multi-layer tube is based on the amount or number of cations on the nanoclay mineral surface that can be exchanged by another cation, i.e., the so-called cation exchange capacity (CEC) of the nanoclay material. It is usually expressed as milliequivalents per 100 g of clay (meq / 100 g clay), the value of which is equal to cmol(+) / kg, where mol(+) represents the number of moles of charge. The CEC is measured by replacing all bound cations with a concentrated solution of another cation and then measuring the amount of the replaced cations or the retained added cations. Barium (Ba 2+ ) and ammonium (NH 4+ ) can be used as exchange cations.

[0064] Preferably, the amount of nano-clay present in at least one layer of the multi-layer tube is at least 80 meq / 100 g of clay, preferably at least 85 meq / 100 g of clay, preferably at least 90 meq / 100 g of clay, preferably at least 95 meq / 100 g of clay, preferably at least 100 meq / 100 g of clay. Preferably, the amount of nano-clay present in at least one layer of the multi-layer tube is at most 110 eq / 100 g of clay, preferably at most 115 meq / 100 g of clay, preferably at most 120 meq / 100 g of clay, preferably at most 125 meq / 100 g of clay, preferably at most 130 meq / 100 g of clay, preferably at most 135 meq / 100 g of clay, preferably at most 140 meq / 100 g of clay. Preferably, the amount of nano-clay present in at least one layer of the multi-layer tube is at a concentration between 90 meq / 100 g of clay and 125 meq / 100 g of clay. In contrast, the unmodified Na + clay has a CEC value of 92.6 meq / 100 g of clay.

[0065] Those skilled in the art will recognize that the dimensions of the multi-layer tubes according to the present invention will vary depending on the amount of fluid they are designed to transport or the type of dwelling they are intended for, but will preferably have an outer tube diameter in the range from 15 mm to 90 mm, more preferably in the range from 16 mm to 75 mm. Accordingly, the total outer wall thickness including the different layers of the multi-layer tube is in the range preferably from 1.5 mm to 9 mm, more preferably from 2 mm to 7.5 mm.

[0066] Preferably, the thickness of the first PE-RT layer is at least 0.5 mm, preferably at least 0.6 mm, preferably at least 0.7 mm, preferably at least 0.8 mm, preferably at least 0.9 mm, preferably at least 1.0 mm, preferably at least 1.1 mm, preferably at least 1.2 mm, preferably at least 1.3 mm, preferably at least 1.4 mm, preferably at least 1.5 mm, preferably at least 1.6 mm, preferably at least 1.7 mm, preferably at least 1.8 mm, preferably at least 1.9 mm, preferably at least 2.0 mm, preferably at least 2.1 mm, preferably at least 2.2 mm, preferably at least 2.3 mm, preferably at least 2.4 mm or preferably at least 2.5 mm. Preferably, the thickness of the first PE-RT layer is at most 6.5 mm, preferably at most 6.6 mm, preferably at most 6.7 mm, preferably at most 6.8 mm, preferably at most 6.9 mm, preferably at most 7.0 mm, preferably at most 7.1 mm, preferably at most 7.2 mm, preferably at most 7.3 mm, preferably at most 7.4 mm, preferably at most 7.5 mm, preferably at most 7.6 mm, preferably at most 7.7 mm, preferably at most 7.8 mm, preferably at most 7.9 mm, preferably at most 8.0 mm, preferably at most 8.1 mm, preferably at most 8.2 mm, preferably at most 8.3 mm, preferably at most 8.4 mm or preferably at most 8.5 mm. Preferably, the thickness of the first PE-RT layer is in the range of from 1.3 mm to 7.2 mm. This is good because the first PE-RT layer (the inner layer of the pipe) is made as thick as possible to allow the outer layer (the second PE-RT layer) of the multi-layer pipe to be as thin as possible. Also, a preferably thinner outer layer helps with compatibility with certain external fittings.

[0067] Preferably, the thickness of the second PE-RT layer is at least 0.1 mm, preferably at least 0.2 mm, preferably at least 0.3 mm, preferably at least 0.4 mm, preferably at least 0.5 mm, preferably at least 0.6 mm, preferably at least 0.7 mm or preferably at least 0.8 mm. Preferably, the thickness of the second PE-RT layer is at most 0.5 mm, preferably at most 0.6 mm, preferably at most 0.7 mm, preferably at most 0.8 mm, preferably at most 0.9 mm, preferably at most 1.0 mm, preferably at most 1.1 mm, preferably at most 1.2 mm, preferably at most 1.3 mm, preferably at most 1.4 mm or preferably at most 1.5 mm. Preferably, the thickness of the second PE-RT layer is in the range of from 0.1 mm to 0.9 mm. The thickness of the second PE-RT layer is chosen to be as thin as possible so that, in the case where a nanoclay layer is present in the layer, the second PE-RT layer (outer) is more compatible with certain external fittings.

[0068] Preferably, the thickness of the UHMWPE layer is at least 0.1 mm, preferably at least 0.2 mm, preferably at least 0.3 mm, preferably at least 0.4 mm or preferably at least 0.5 mm. Preferably, the thickness of the UHMWPE layer is at most 0.5 mm, preferably at most 0.6 mm, preferably at most 0.7 mm, preferably at most 0.8 mm, preferably at most 0.9 mm, preferably at most 1.0 mm, preferably at most 1.1 mm, preferably at most 1.2 mm, preferably at most 1.3 mm, preferably at most 1.4 mm or preferably at most 1.5 mm. Preferably, the thickness of the UHMWPE layer is in the range of 0.1 mm to 0.7 mm.

[0069] Preferably, the UHMWPE layer comprises UHMWPE tapes or fibres. The UHMWPE layer comprising UHMWPE tapes or fibres provides a thicker reinforcement layer for the multi-layer tube.

[0070] Preferably, the UHMWPE tape layer comprises two layers of tapes, with one layer on top of the other. In this way, the UHMWPE layer is formed by several layers of UHMWPE tapes, which increases the strength of the UHMWPE tapes while maintaining the overall flexibility of the UHMWPE tape layer itself and the overall flexibility of the multi-layer tube.

[0071] Preferably, the two layers of tapes have an overlap angle of at least 20°, preferably at least 25°, preferably at least 30°, preferably at least 35°, preferably at least 40°, preferably at least 45°, preferably at least 50° or preferably at least 55° between them. Preferably, the two layers of tapes have an overlap angle of at most 60°, preferably at most 65°, preferably at most 70°, preferably at most 75°, preferably at most 80°, preferably at most 85° or preferably at most 90° between them. Preferably, the two layers of tapes have an overlap angle ranging from 40° to 70° between them. It has been found that when the two layers of tapes have an overlap angle within this range between them, this maximizes the strength and flexibility of the UHMWPE tape layer.

[0072] Preferably, the multi-layer tube further comprises an adhesive layer disposed between the first PE-RT layer and the UHMWPE layer, and / or an adhesive layer disposed between the second PE-RT layer and the UHMWPE layer. Although not essential for the present invention, the additional adhesive layer (whether present between the first PE-RT layer and the UHMWPE layer, and / or between the second PE-RT layer and the UHMWPE layer) allows the corresponding first PE-RT layer or second PE-RT layer and the UHMWPE layer to adhere more strongly to each other, minimizing the seam opening between the layers, which can be exploited by blistering or bulging phenomena.

[0073] Preferably, the nanoclay is dispersed in a bonding layer disposed between the first PE-RT layer and the UHMWPE layer, and / or the nanoclay is dispersed in a bonding layer disposed between the second PE-RT layer and the UHMWPE layer. In this way, at least one PE-RT layer is located between the internal flow path of the multilayer pipe and the UHMWPE layer to minimize the potential water vapor diffusing through the multiple layers of the multilayer pipe, which could otherwise cause blistering or bulging.

[0074] Preferably, at least one bonding layer is formed of high density polyethylene (HDPE), maleic anhydride grafted HDPE (HDPE-g-MA), low density polyethylene (LDPE), maleic anhydride grafted LDPE (LDPE-g-MA), or a combination thereof. The bonding layer formed of HDPE or LDPE, whether grafted with maleic anhydride or otherwise, provides improved bonding between the first PE-RT layer and the UHMWPE layer, or between the second PE-RT layer and the UHMWPE layer.

[0075] Preferably, the thickness of at least one bonding layer is at least 0.1 mm, preferably at least 0.2 mm, preferably at least 0.3 mm, preferably at least 0.4 mm, preferably at least 0.5 mm, preferably at least 0.6 mm, preferably at least 0.7 mm, or preferably at least 0.8 mm. Preferably, the thickness of the second PE-RT layer is at most 0.5 mm, preferably at most 0.6 mm, preferably at most 0.7 mm, preferably at most 0.8 mm, preferably at most 0.9 mm, preferably at most 1.0 mm, preferably at most 1.1 mm, preferably at most 1.2 mm, preferably at most 1.3 mm, preferably at most 1.4 mm, or preferably at most 1.5 mm. Preferably, the thickness of at least one bonding layer is in the range of 0.1 mm to 0.9 mm. More preferably, the thickness of at least one bonding layer is in the range of 0.2 mm to 0.6 mm. The thickness of at least one bonding layer is selected to not be too thick, otherwise it affects the long-term characteristics of the multilayer pipe. For example, when at least one bonding layer is an LDPE-based bonding layer, it has a lower melting point compared to the layers composed of PE-RT or UHMWPE. Generally, the thickness of at least one bonding layer is at most 10% of the total pipe diameter.

[0076] Preferably, at least one bonding layer does not contain ethylene vinyl alcohol (EVOH). EVOH is known to be a strong barrier against oxygen and gases, it is difficult to manufacture and thus more expensive. The use of EVOH also presents disadvantages in terms of recyclability, and the fact that when using EVOH, additional bonding layers are required to bond the different layers of the pipe together.

[0077] Preferably, the multilayer tube does not contain aluminum. A polymeric multilayer tube that does not include aluminum retains good flexibility and can thus be used in a variety of scenarios where flexibility is useful, for example, for transporting liquids around corners.

[0078] Preferably, the multilayer tube has a density of less than 1 g / cm 3 . This is advantageous because it is less expensive and easier to transport than conventional metal or concrete alternatives.

[0079] Accordingly, the present invention provides a multilayer tube for transporting hot water in a residence, the tube comprising a plurality of concentric layers of polymeric material, the layers being:

[0080] an inner first PE-RT layer;

[0081] a UHMWPE layer; and

[0082] an outer second PE-RT layer containing a nanoclay material.

[0083] A multilayer tube comprising a nanoclay outer layer provides an oxygen barrier adjacent to the surrounding environment to minimize potential water vapor diffusing through the multiple layers of the multilayer tube, which could otherwise cause blistering or bulging.

[0084] Alternatively, the present invention provides a multilayer tube for transporting hot water in a residence, the tube comprising a plurality of concentric layers of polymeric material, the layers being:

[0085] an inner first PE-RT layer;

[0086] a UHMWPE layer containing a nanoclay material; and

[0087] an outer second PE-RT layer.

[0088] This is advantageous because when the nanoclay is present in the UHMWPE layer, the water absorption of the nanoclay decreases with increasing nanoclay concentration. Such an improvement is attributed to the reduced water absorbency of the organoclay composite, resulting in less softening of the UHMWPE polymer layer and leading to better abrasion resistance.

[0089] Alternatively, the present invention provides a multilayer tube for transporting hot water in a residence, the tube comprising a plurality of concentric layers of polymeric material, the layers being:

[0090] an inner first PE-RT layer;

[0091] a first LDPE bonding layer containing a nanoclay material;

[0092] a UHMWPE layer;

[0093] A second LDPE bonding layer comprising a nanoclay material; and

[0094] An outer second PE-RT layer.

[0095] In this embodiment, at least one PE-RT layer is located between the internal flow path of the multi-layer pipe and the UHMWPE layer to minimize the potential water vapor that diffuses through the multiple layers of the multi-layer pipe, which could otherwise cause blistering or bulging. The bonding layer formed of HDPE or LDPE, whether grafted with maleic anhydride or otherwise, provides improved bonding between the first PE-RT layer and the UHMWPE layer, or between the second PE-RT layer and the UHMWPE layer.

[0096] Alternatively, the present invention provides a multi-layer pipe for transporting hot water in a residence, the pipe being composed of multiple concentric layers of polymer materials, which are:

[0097] An inner first PE-RT layer;

[0098] An LDPE bonding layer;

[0099] A UHMWPE layer; and

[0100] An outer second PE-RT layer comprising a nanoclay material.

[0101] This is beneficial because when nanoclay is present in the UHMWPE layer, the water absorption of the nanoclay decreases as the nanoclay concentration increases. Such improvement is attributed to the reduced water absorbency of the organoclay composite material, resulting in less softening and plasticization of the UHMWPE polymer layer and better wear resistance. In addition, at least one PE-RT layer is located between the internal flow path of the multi-layer pipe and the UHMWPE layer to minimize the potential water vapor that diffuses through the multiple layers of the multi-layer pipe, which could otherwise cause blistering or bulging. The bonding layer formed of HDPE or LDPE, whether grafted with maleic anhydride or otherwise, provides improved bonding between the first PE-RT layer and the UHMWPE layer, or between the second PE-RT layer and the UHMWPE layer.

[0102] Preferably, a portion of the UHMWPE layer may be dispersed in at least one of the first PE-RT layer or the second PE-RT layer. In cases where the UHMWPE layer comprises UHMWPE tapes or fibres, preferably, the UHMWPE tapes or fibres are dispersed in at least one of the first PE-RT layer or the second PE-RT layer to form a matrix. Those skilled in the art will understand that, in a first embodiment according to the invention, in cases where a portion of the UHMWPE layer may be dispersed in at least one of the first PE-RT layer or the second PE-RT layer, the nanoclay may still be dispersed in at least one of the first PE-RT layer or the second PE-RT layer or dispersed in the UHMWPE layer. In this way, at least one of the first PE-RT layer or the second PE-RT layer of the multi-layer tube may thus also comprise a mixture of UHMWPE tapes or fibres and at least one nanoclay material.

[0103] Accordingly, a second embodiment of the invention relates to a method of manufacturing a multi-layer polymer tube according to any one of the preceding claims, the method comprising the steps of:

[0104] Melt-extruding a first PE-RT layer to form the longitudinal axis of the tube;

[0105] Melt-extruding a UHMWPE layer over the first PE-RT layer; and

[0106] Applying a second PE-RT layer over the UHMWPE layer.

[0107] This method is considered to be cheaper and easier to implement in order to manufacture a multi-layer tube according to the first embodiment of the invention, because i) fewer layers are required to form the multi-layer tube, ii) those layers required can be easily bonded and adhered together due to the similar chemical properties of the individual layers, and iii) the whole process can be carried out using prior art.

[0108] Preferably, the method of manufacturing a multi-layer polymer tube comprises the following additional steps:

[0109] Applying a bonding layer over the first PE-RT layer before melt-extruding the UHMWPE layer;

[0110] and / or

[0111] Applying a bonding layer over the UHMWPE layer before applying the second PE-RT layer.

[0112] Incorporating one or more additional bonding layers improves the bonding between the existing layers of the multi-layer tube to increase the overall strength and flexibility of the multi-layer tube while minimising the potential water vapour diffusing through the multiple layers of the multi-layer tube.

[0113] The PE-RT polymer is resilient and allows for considerable elastic deformation. In some applications, it is desirable that the multi-layer polymer tube of the present invention is deformable, and bending is a typical requirement in applications, but it does not show significant elastic recovery during bending. Therefore, preferably, the resilience of the multi-layer tube of the present invention is reduced. The reduction of resilience can be conveniently achieved by using fillers, which can be referred to as bulk fillers. However, the use of nano-clay (functional filler) and its beneficial effects (as described above) can be adversely affected by the introduction of other fillers, which refer to physical particles other than the polymer. Therefore, preferably, the resilience (elastic recovery) of the multi-layer tube of the present invention is limited without providing additional solid materials to the UHMWPE layer. It has been found that the desired properties can be achieved by adding fillers to the PE-RT component. However, it has been found that not all fillers are suitable, and certainly not all fillers are equally effective in combination with nano-clay.

[0114] Fillers that are materials having a larger particle size than the nano-clay filler, for example, having a particle size of 0.5 μm or more, preferably less than 40 μm, more preferably in the range of 1 μm to 6 μm (D 50 ). Larger particles at higher filler levels result in a weaker polymer composite. Such fillers can be referred to as bulk fillers to distinguish them from nano-clay, although nano-clay can be technically considered a filler in terms of particle size, and all are functional fillers with desired effects. Those skilled in the art generally do not consider (expensive) functional components such as nano-clay as fillers / bulk fillers because that is not their function.

[0115] In the present invention, inorganic fillers are preferred because any inorganic filler dissolves into the supply water such as drinking water, inorganic fillers have inherently lower toxicity and higher thermal stability, especially considering that low-level decomposition at elevated temperatures over time can reduce the structural integrity of the tube or increase the potential release of toxins into the water.

[0116] Preferred inorganic fillers suitable for inclusion in a PE-RT layer of the present invention include:

[0117] Talc – Mg3Si4O 10 (OH)2; Calcium carbonate – CaCO3, such as in the form of chalk; Kaolin – Al2Si2O5(OH)4;

[0118] Wollastonite – CaSiO3; Muscovite – KAl2(Si3A1O 10 )(OH)2; Phlogopite – KMg3(AlSi3O 10)(OH)2; glass beads or fibers – SiO2; calcium silicate – Ca2SiO4, such as diatomaceous earth and barium sulfate – BaSO4.

[0119] Preferred inorganic fillers are talc – Mg3Si4O 10 (OH)2 and calcium carbonate – CaCO3, such as in the form of chalk.

[0120] The most preferred filler is talc, as this provides the greatest reduction in the resilience recovery of the bent tube in pipes including the PE / RT layer using the filler.

[0121] Type B or C talc that preferably meets the ISO 3262 quality standard, and type D talc with a higher loss on ignition provides a weaker polymer compound.

[0122] In the present invention, the filler can be added to the first (inner) PE-RT layer at a level of 5% to 60% by weight. To reduce the elastic recovery of the bent tube, the preferred level of the filler added is between 10% and 45% by weight. Higher levels of addition can show a reduction in tube strength, and a more preferred filler addition amount is 20% to 40%.

[0123] Alternatively, a filler can be added at a level between 10% and 60% by weight to the second PE-RT layer arranged around the UHMWPE layer.

[0124] The filler can be used in both PE-RT layers.

[0125] However, the filler incorporated into the PE-RT as the inner layer can potentially come into contact with the water in the tube, and for drinking water, it may be preferred to have the filler in the second PE-RT layer, even if this is less effective.

[0126] Regarding the desired characteristic that the tube of the present invention retains its deformation after bending (longitudinal bending), it has been found that incorporating the filler into the first (inner) PE-RT layer is more effective. Incorporating the filler into the second (outer) layer is also effective in reducing the resilience recovery after tube bending, but the effect is relatively weaker.

[0127] When nano-clay is incorporated into the PE-RT layer, it is preferably incorporated into the inner layer to reduce the gas (moisture) transport from the contents of the tube. The presence of the filler (i.e., the bulk filler with nano-clay) is disadvantageous because it increases the gas permeability, so the bulk filler is preferably in the other PE-RT layer. Therefore, the bulk filler is preferably placed in the outer PE-RT layer.

[0128] The layer comprising the nano-clay preferably does not include other solid component polymer additives other than the nano-clay. The layer comprising the nano-clay preferably consists of a polymer and the nano-clay, and optionally, the trace additives are less than 5%. The layer comprising the filler preferably consists of the filler and the polymer, and optionally, the trace additives are less than 5% of the total weight.

[0129] As described herein, the plastic pipe of the present invention is preferably configured for hot water supply (such as 30°C to 80°C), and can therefore withstand pressures greater than 1 bar in this temperature range, such as in the range of 1 bar to 8 bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0130] The description is made with reference to the accompanying drawings, in which the same reference numerals are intended to denote the same components, and in which:

[0131] Figure 1 represents a cross-sectional view of a multi-layer pipe according to a first embodiment of the present invention;

[0132] Figure 2 represents a cross-sectional view of a multi-layer pipe according to an alternative first embodiment of the present invention;

[0133] Figure 3 represents a cross-sectional view of a multi-layer pipe according to an alternative first embodiment of the present invention;

[0134] Figure 4 represents a cross-sectional view of a multi-layer pipe according to an alternative first embodiment of the present invention;

[0135] Figure 5 shows tools and methods for pipe bending, such as those used in test methods; and

[0136] Figure 6 shows a method for measuring the change in pipe bending relaxation over time when used in test methods.

[0137] The following abbreviations are widely used throughout the specification.

[0138] Abbreviation

[0139] PE-RT: Polyethylene of raised temperature resistance;

[0140] HDPE: High density polyethylene;

[0141] LDPE: Low density polyethylene;

[0142] UHMWPE: Ultra-high molecular weight polyethylene;

[0143] (HD / LD)PE-g-MA: (High density / low density) polyethylene grafted maleic anhydride.

[0144] For the avoidance of any doubt, the corresponding definitions of each acronym used hereinafter are provided.

[0145] Definitions

[0146] PE-RT is a polyethylene (PE) resin in which the molecular structure has been designed such that a sufficient amount of linking chains are incorporated to allow operation at elevated or raised temperatures (RT). The linking chains "link" the crystalline structures in the polymer, resulting in improved properties such as high temperature strength and properties, chemical resistance, and resistance to slow crack growth. Suitable grades of PE-RT include Dowlex 2388, Dowlex 2344, Dowlex 2355, and Dowlex 2377 from The Dow Chemical Company (Dow); Hostalen 4731B, ex Hostalen 4131B from Lyondell-Basell Industries N.V.; Daelim XP 9020 from Daelim Industrial Co., Ltd.; Hanwha M7037 from Hanwha Corporation; Lucene SP988 from LG Chem Ltd.; and Yuclair DX800 from SKC Co., Ltd.

[0147] HDPE or high-density polyethylene (PEHD) is a thermoplastic polymer prepared from the monomer ethylene. The high strength-to-density ratio of HDPE is known. HDPE pipes do not rust, rot, or corrode and are resistant to biological growth. This means extended service life and long-term cost savings. The density range of HDPE is from 0.93 g / cm 3 to 0.97 g / cm 3 . Although the density of HDPE is only slightly higher than that of low-density polyethylene, HDPE has few branches, resulting in stronger intermolecular forces and tensile strength (38 MPa vs. 21 MPa) than LDPE. The strength difference exceeds the density difference, giving HDPE a higher specific strength. It is also harder, more opaque, and can withstand slightly higher temperatures (120 °C / 248 °F for short periods). Unlike polypropylene, high-density polyethylene cannot withstand the autoclaving conditions typically required. The absence of branches is ensured by the appropriate selection of catalysts (e.g., Ziegler-Natta catalyst) and reaction conditions. HDPE is resistant to many different solvents, so it cannot be glued, and pipe joints must be made by welding, but this makes pipes constructed of HDPE ideally suited for transporting potable water and wastewater (rainwater and sewage).

[0148] LDPE is also a thermoplastic made from the monomer ethylene. LDPE has a density of 0.917 g / cm 3 to 0.93 g / cm 3Density range limitation. It is not reactive at room temperature, except towards strong oxidants; some solvents cause it to swell. It can continuously withstand temperatures of 65 °C (149 °F) and 90 °C (194 °F) for short periods of time. Made in translucent and opaque variants, it is quite flexible and tough. LDPE has more branches (about 2% of carbon atoms) than HDPE, so its intermolecular forces (instantaneous dipole-induced dipole attraction) are weaker, its tensile strength is lower, and its resilience is higher. The side branches mean that its molecules are less closely packed and less crystalline, and thus its density is lower. When exposed to consistent sunlight, the plastic produces significant amounts of two greenhouse gases: methane and ethylene. Due to its lower density (high branching), it decomposes more easily than other plastics; when this occurs, the surface area increases. The production of these trace gases from the original plastic increases with the surface area and time, making LDPE emit greenhouse gases at a less sustainable rate than other plastics. When incubated in air, LDPE emits methane and ethylene at rates approximately 2 times and 76 times higher, respectively, than in water.

[0149] UHMWPE is a polyethylene polymer mainly comprising ethylene-derived units, and in some embodiments, UHMWPE is a homopolymer of ethylene. Optionally, UHMWPE can include additional α-olefins such as, but not limited to, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, and 3-methyl-1-pentene. Suitable UHMWPE can have a weight-average molecular weight (Mw) of about 1,500,000 g / mol or greater, about 1,750,000 g / mol or greater, about 1,850,000 g / mol or greater, or about 1,900,000 g / mol or greater. Due to the metallocene-catalyst-based synthesis method, these molecules are several orders of magnitude longer than those of familiar HDPE, resulting in UHMWPE molecules typically having 100,000 to 250,000 monomer units per molecule compared to 700 to 1,800 monomers for HDPE. Examples of commercially available UHMWPE include MIPLEON TMTM XM-220, MIPLEON TM XM-330 (both purchased from Mitsui Chemical), Ticona GUR TM 4170 (purchased from Celanese in Dallas, Texas, USA), UTEC3040 (Braskem), LUBMER TM 5000 and LUBMER TM 5220 (both purchased from Mitsui Chemical).

[0150] Suitable UHMWPE can be in the form of powder or pellets, and / or have an average particle size of about 75 μm or less, about 70 μm or less, or about 65 μm or less. Additionally or alternatively, suitable UHMWPE can have an average particle size of 10 μm or greater, 15 μm or greater, 20 μm or greater, or 25 μm or greater. Additionally or alternatively, suitable UHMWPE can have an average particle size of about 40 μm to about 75 μm, such as about 50 μm to about 70 μm, or about 55 μm to 65 μm. Additionally or alternatively, suitable UHMWPE can have an average particle size of about 10 μm to about 50 μm, such as about 15 μm to about 45 μm, about 20 μm to about 40 μm, or about 25 μm to about 30 μm.

[0151] The particle size in the present invention is determined by ASTM E2834-12 (2022), and a suitable device is the NanoSight NS300 of Malvern Panalytical(R). This applies to nano-clay. For particles larger than the nano-scale, such as bulk fillers, the particle size can be determined using the Mastersizer 3000 of Malvern Panalytical.

[0152] Water can be used as a medium for suspending solids in the analysis. Measurements are carried out at 25 °C unless the method otherwise requires. The preferred particle size measurement is D3,2 unless the method otherwise requires. The particle size of plastics can be measured using ASTM D7486-14.

[0153] The following reproduced structure is for reference. PE-g-MA is a compatibilizer for polymer blends, and the polymer blends are used as a support for polar substances to non-polar substances:

[0154]

[0155] It is known that introducing or mixing PE-g-MA with LDPE / HDPE produces blends with higher thermal stability. This is a desired property for forming multi-layer tubes. Detailed Description

[0156] Tube bending method and test.

[0157] This is combined Figure 5 and Figure 6 shown.

[0158] The present invention utilizes a method for determining the retention of bends generated by manually bending using a bending tool in a tube. The retention of the bend depends on the resilience of the tube in question. An ideal tube retains its bend to the degree of bend of I and does not return to linearity over time.

[0159] A tube 50 with a diameter of 20 mm having such a construction as described in the previous example is fixed in a tube bending tool 100.

[0160] The tube bending tool 100 is a conventional type known in the industry and includes two handles 108, 110 which are rotatable about a pivot 106. The pivot 106 acts as an axle for a wheel 102 which, when viewed from the side, has a groove to receive the tube 50 (not shown in the figure). The pivot also has a bracket 120 which extends perpendicular to the first handle 108 and which has a clamping portion to hold the tube 50 in place against the wheel 102. When the second handle 110 which includes a forming piece (the rectangle shown in the middle of the handle) rotates, the tube 50 is held by the clamping portion of the bracket 120 and thus conforms to the circumference (the inside of the groove) of a wheel having a diameter of 12 cm. The handles 108, 120 rotate to become collinear so as to perform a 90° bend.

[0161] The tube 50 is now a bent tube 52 and it is placed on a measuring table with a reference line 120 having a rod perpendicular to the tube 52 such that when the tube 52 is slack and deviates from the vertical bend to provide a tube 54, the deviation angle 122 is recorded. This deviation angle is recorded over time. The experiment is carried out at an ambient temperature taken as 20 °C. The rate of bending provides a bend in about 15 seconds.

[0162] The angle 122 is recorded immediately after bending (i.e., the tube is released from the tool and placed on a flat surface, taking about 10 seconds), 30 minutes later, 24 hours later and 2 weeks later. The length of the tube is 50 cm although this is not critical.

[0163] Unless otherwise stated, the wall thickness of all tube examples herein is 3 mm and the diameter is 20 mm. Any UHMWPE layer is a tape 0.25 mm thick. Any plurality of PE-RT layers have equal thickness. The thickness of any bonding layer can be taken as 0.25 mm. Unless otherwise specified, the PE-RT used is Dowlex 2388.

[0164] Examples 2 to 5 and Reference 1

[0165] Figure 1 A cross-sectional view of a multi-layer tube (10) according to a first embodiment of the present invention is shown. More specifically, Figure 1Shows a multi-layer pipe (10) having a plurality of concentric polymer material layers that are sequentially arranged on top of each other and consist of a first PE-RT layer (12) forming the longitudinal axis of the pipe (10), a UHMWPE layer (14) containing dispersed UHMWPE bands / fibers arranged around the first PE-RT layer (12), and a second PE-RT layer (16) including a filler material arranged around the UHMWPE layer (14). The nano-clay material in the second PE-RT layer (16) is surface-modified montmorillonite with the chemical formula (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), a hydrated sodium calcium aluminum magnesium hydroxide silicate, the surface of which is modified with a quaternary ammonium salt 20A.

[0166] Example 1 has 6 variants. There is or is not a filler in each PE-RT layer, and when the filler is present, it is present in the first or second layer and at a content of 11.25% or 22.5%.

[0167] Unless otherwise specified, the talc filler in all examples is Granic 282(TM) masterbatch from the CRT Group, which contains 75% talc (D 50 4μm) in PE and contains a filler providing, for example, 22.5%. Unless otherwise specified, the percentage content is based on the weight of the layer in which the filler is present.

[0168] The multi-layer pipe (10) is prepared by the following steps: melt-extruding the first PE-RT layer (12) forming the longitudinal axis of the pipe (10), melt-extruding the UHMWPE layer (14) around the first PE-RT layer (12), and applying a second (outer) PE-RT layer (16) containing nano-clay around the UHMWPE layer (14).

[0169] Reference 1, Examples 2 to 5 Inner PE-RT layer Outer PE-RT layer 1 No filler No filler 2 11.25% talc No filler 3 22.5% talc No filler 4 No filler 11.25% talc 5 No filler 22.5% talc

[0170] Example 6

[0171] It is the same as Example 5, wherein the nano-clay material in the second PE-RT layer (16) is surface-modified montmorillonite with the chemical formula (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), a hydrated sodium calcium aluminum magnesium hydroxide silicate, the surface of which is modified with a quaternary ammonium salt 20A.

[0172] Examples 8 and Reference 7

[0173] Figure 2 A cross-sectional view of a multi-layer pipe (20) according to an alternative first embodiment of the present invention is shown. More specifically, Figure 2 A multi-layer pipe (20) is shown with reference numeral 7. The multi-layer pipe (20) has a plurality of concentric polymer material layers, which are sequentially arranged on top of each other and consist of a first PE-RT layer (22) forming the longitudinal axis of the pipe (20), a UHMWPE layer (24) containing nano-clay material arranged around the first PE-RT layer (22), and a second PE-RT layer (26) arranged around the UHMWPE layer (24). The nano-clay material in the UHMWPE layer (24) is surface-modified montmorillonite with the chemical formula (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), a hydrated sodium calcium aluminum magnesium silicate hydroxide, the surface of which is modified with a quaternary ammonium salt 20A.

[0174] In Example 8, the pipe is as in reference numeral 7, wherein in the first PE-RT layer (16), the Granic 282 masterbatch containing 75% talc powder in the PE contains 22.5% filler.

[0175] The multi-layer pipe (20) is prepared by the following steps: melt-extruding the first PE-RT layer (22) forming the longitudinal axis of the pipe (20), melt-extruding the UHMWPE layer (24) containing nano-clay around the first PE-RT layer (22), and applying a second (outer) PE-RT layer (26) around the UHMWPE layer (24).

[0176] Example 10 and reference numeral 9

[0177] Figure 3 A cross-sectional view of a multi-layer pipe (30) according to an alternative first embodiment of the present invention is shown. More specifically, Figure 3Shows a multilayer pipe (30) of reference 9, the multilayer pipe (30) having a plurality of concentric polymer material layers, the plurality of concentric polymer material layers being sequentially arranged on top of each other and consisting of a first PE-RT layer (32) forming the longitudinal axis of the pipe (30), a first LDPE bonding layer (38a) including a nanoclay material disposed around the first PE-RT layer (32), a UHMWPE tape layer (34) disposed around the first LDPE bonding layer (38a), a second LDPE bonding layer (38b) containing a nanoclay material disposed around the UHMWPE tape layer (34), and a second PE-RT layer (36) disposed around the second LDPE bonding layer (38b). The nanoclay material in each of the first LDPE bonding layer (38a) and the second LDPE bonding layer (38b) is surface-modified montmorillonite, the chemical formula of which is (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), a hydrated sodium calcium aluminum magnesium silicate hydroxide, the surface of which is modified with a quaternary ammonium salt 20A.

[0178] In Example 10, the pipe is as in reference 9, wherein in the first PE-RT layer 16, the Granic 282 masterbatch containing 75% talc in the PE contains 22.5% filler.

[0179] The multilayer pipe (30) is prepared by the following steps: melt-extruding the first PE-RT layer (32) forming the longitudinal axis of the pipe (30), applying the first LDPE bonding layer (38a) containing nanoclay around the first PE-RT layer (32), applying the UHMWPE tape layer (34) by winding the UHMWPE tape layer around the first LDPE bonding layer (38a), applying the second LDPE bonding layer (38b) containing nanoclay around the UHMWPE tape layer (34), and applying the second (outer) PE-RT layer (36) around the second LDPE bonding layer (38b).

[0180] Example 12 and reference 11

[0181] Figure 4 Shows a cross-sectional view of a multilayer pipe (40) according to an alternative first embodiment of the present invention. More specifically, Figure 4Shows a multi-layer pipe (40) of Reference 11. The multi-layer pipe (40) has a plurality of concentric polymer material layers, which are sequentially arranged on top of each other and consist of a first PE-RT layer (42) forming the longitudinal axis of the pipe (40), a first LDPE bonding layer (48a) arranged around the first PE-RT layer (42), a UHMWPE tape layer (44) arranged around the first LDPE bonding layer (48a), a second LDPE bonding layer (48b) arranged around the UHMWPE layer (44), and a second PE-RT layer (46) including a nanoclay material arranged around the second LDPE bonding layer (48b). The nanoclay material is surface-modified montmorillonite with the chemical formula (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O), a hydrated sodium calcium aluminum magnesium silicate hydroxide, the surface of which is modified with quaternary ammonium salt 20A.

[0182] In Example 12, the pipe is as in Reference 11, wherein in the first PE-RT layer (16), the Granic 282 masterbatch containing 75% talc in PE contains 22.5% filler provided.

[0183] The multi-layer pipe (40) is prepared by the following steps: forming a first PE-RT layer (42) forming the longitudinal axis of the pipe (40) by melt extrusion, applying a first LDPE bonding layer (48a) around the first PE-RT layer (42), applying a UHMWPE layer (44) by winding a UHMWPE tape layer around the first LDPE bonding layer (48a), applying a second LDPE bonding layer (48b) around the UHMWPE tape layer (44), and applying a second (outer) PE-RT layer (46) containing nanoclay around the second LDPE bonding layer (48b).

[0184] Examples 14 to 20 and Reference 13

[0185] Reference 13 is a single-layer PE-RT pipe. The pipe is prepared by forming a first PE-RT layer of the longitudinal axis of the pipe by melt extrusion.

[0186] Examples 14 and 15 represent containing 11.25% or 22.5% filler in PE-RT respectively.

[0187] The chalk filler is Mastercal 283 of Kilwaugher Lime introduced as a masterbatch into PE.

[0188] Reference 13, Examples 14 to 17 PE-RT 13 No filler 14 5.6% talc 15 11.25% talc 16 22.5% talc 17 33.75% talc 18 45% talc 19 11.25% chalk 20 22.5% chalk

[0189] Rectangular blank specimens measuring 1 cm by 15 cm by 1 mm were also made from PE-RT and PE-RT with fillers, and the following parameters were measured using an Instron(TM) testing machine, such as a 6800 series machine.

[0190]

[0191] Examples 21 and 22

[0192] Example 21 is like Example 13 and has a UHMWPE tape layer on the outer surface of the tube.

[0193] Example 22 is like Example 16 and has a UHMWPE tape layer on the outer surface of the tube.

[0194] Tube bending, preliminary test results

[0195] Example tube After bending 30 minutes 24 hours 2 weeks 1R Fail - - - 2 Pass Pass -- Fail 3 Pass+ Pass+ Pass Pass 4 Pass Pass -- Fail 5 Pass+ Pass+(pass+) Pass Pass 6 Pass Pass Pass Pass 7R Fail - - - 8 Pass Pass Pass Fail 9R Fail - - - 10 Pass Pass Pass Pass 11R Fail - - - 12 Pass+ Pass Pass Pass 13R Fail - - - 14 Fail 15 Pass Pass -- Fail 16 Pass+ Pass Pass Pass 17 Pass+ Pass+ Pass Pass 18* Pass+ - - - 19 Pass Fail - - 20 Pass Pass Pass Fail 21R Fail - - - 22 Pass Pass Pass Fail

[0196] An acceptable level of elasticity (i.e., resilience recovery) was taken as 5° or less. An angle greater than this was marked as a failure, and no further measurements were provided. R represents the reference sample, i.e., without fillers. Pass is a bend of 5° or less. Pass + is no change within the error, taken as a change in bend of 1°. * Loss of tube strength during bending.

[0197] Results summary

[0198] Initial results showed that PE-RT tubes have resilience and return at least to some extent to their initial shape when bent. Similarly, multi-layer tubes containing a large number of PE-RT layer components have similar resilience. This is even more so when a UHMWPE layer is included. The presence of nanoclay is not an effective material for reducing this resilience. Adding talc or chalk as fillers reduces the resilience, and when the tube is bent, the tube is more likely to maintain its curvature. As shown by the test results, based on the added weight, talc is more effective than chalk. However, adding 22.5% by weight of chalk significantly reduces the resilience recovery of the bent tube. However, adding 5.6 of talc is ineffective, and adding 11.25% or more of talc is effective. However, the most effective range of talc in the PE-RT layer of the tube seems to be between 22.5% and 33.75%. High levels of addition are also effective for tube bending but seem to affect the final strength of the tube.

Claims

1. A plastic pipe for use in a piping system and manually bendable by 90°, the pipe comprising: a) A first polyethylene layer comprising high temperature resistant polyethylene (PE-RT) forming the longitudinal axis of the pipe; The PE-RT layer contains an inorganic filler in an amount between 5% and 60% by weight, the inorganic filler having a particle size ranging from 0.5 μm to 40 μm (D 50 ) with an average particle size.

2. The tube according to claim 1, wherein, The inorganic filler is selected from one or more of talc, calcium carbonate, kaolin, wollastonite, muscovite, phlogopite, glass beads or fibers, calcium silicate, and barium sulfate—BaSO4 and mixtures thereof.

3. The tube according to claim 2, wherein, The inorganic filler is selected from talc or calcium carbonate.

4. The tube according to any one of the preceding claims, wherein, The pipe does not contain aluminum or copper.

5. The pipe according to any one of claims 1 to 4, further comprising: b) A ultra-high molecular weight polyethylene (UHMWPE) layer disposed around the first PE-RT layer.

6. The pipe according to any one of claims 1 to 4, further comprising: c) A ultra-high molecular weight polyethylene (UHMWPE) layer disposed within the first PE-RT layer.

7. The pipe according to claim 5 or claim 6, further comprising: d) A second PE-RT layer, and d1) Disposed outside the previously claimed layer b), or d2) Disposed inside the previously claimed layer c).

8. The tube according to any one of the preceding claims, wherein At least one layer of the plurality of layers further comprises a nanoclay material for reducing gas transmission through the plurality of layers.

9. The tube according to any one of the preceding claims, wherein, At least one layer of the plurality of layers that does not contain an inorganic filler comprises a nanoclay material for reducing gas transmission through the plurality of layers.

10. The tube according to claim 8, wherein, The innermost PE-RT layer a) is surrounded by a UHMWPE layer b), which in turn is surrounded by a PE-RT d1) comprising a nanoclay material for reducing gas transmission through the plurality of layers.

11. The tube according to claim 8, wherein, The nanoclay is present in the UHMWPE layer c).

12. The multi-layer tube according to any one of claims 8 to 11, wherein, The amount of the nanoclay is at most 10 wt.% of the corresponding layer in which it is located.

13. The tube according to any one of claims 8 to 12, wherein, The nano-clay is surface-modified montmorillonite, and the surface-modified montmorillonite is a hydrated sodium calcium aluminum magnesium hydroxide with the chemical formula (Na,Ca) 0.33 (Al,Mg)2(Si4O 10 )(OH)2·nH2O).

14. The tube according to any one of the preceding claims, wherein, The thickness of the first PE-RT layer a) is in the range of 1.3 mm to 7.2 mm.

15. The tube according to any one of the preceding claims, wherein, The thickness of the second PE-RT layer b) is in the range of 0.1 mm to 0.9 mm.

16. The tube according to any one of claims 5 to 15, wherein, The thickness of the UHMWPE layer is in the range of 0.1 mm to 0.7 mm.

17. The tube according to any one of claims 5 to 16, wherein, The UHMWPE layer is formed of UHMWPE tapes, and the UHMWPE layer optionally comprises two layers of tapes, one layer on top of the other.

18. The tube according to claim 17, wherein, The two layers of tapes have an overlap angle of 40° to 70° therebetween.

19. The pipe according to any one of claims 5 to 18, further comprising a bonding layer disposed between the first PE-RT layer and the UHMWPE layer, and / or disposed between the second PE-RT layer and the UHMWPE layer.

20. The tube according to any one of the preceding claims has a density of less than 1 g / cm 3 .

21. The tube according to any one of the preceding claims, wherein, The pipe is composed of the layer (claim 1) or multiple layers (claims 2 to 20), and the layer or the multiple layers comprise less than 5% by weight of minor additives.

22. A multi-layer pipe for transporting hot water in a residence, the pipe being composed of concentric layers of polymeric materials, the layers being: The first inner PE-RT layer, the first PE-RT layer comprising an inorganic filler in an amount between 5% and 60% by weight, the inorganic filler having a particle size (D 50 ) with an average particle size from 0.5 μm to 40 μm; UHMWPE layer; and An outer second PE-RT layer containing a nanoclay material.

23. A method of manufacturing a multilayer polymer tube according to any one of claims 5 to 22, the method comprising the steps of: Melting and extruding a first PE-RT layer a) to form the longitudinal axis of the tube; Melting and extruding a UHMWPE layer b) onto the first PE-RT layer; And Applying a second PE-RT layer d1) onto the UHMWPE layer.

24. The method according to claim 23, further comprising the following additional steps: Applying an adhesion layer onto the first PE-RT layer before melting and extruding the UHMWPE layer; and / or Applying an adhesion layer onto the UHMWPE layer before applying the second PE-RT layer.

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