Completely recyclable multilayered hose

Abstract: A recyclable hose comprising a number of mutually connected coaxial layers, comprising a first inner layer having a surface adapted to contact a fluid to be carried, a second reinforcing layer and a third external layer adapted to protect and lock the second reinforcing layer; the second layer being constituted by a material completely compatible and mixable with the polymer or polymer composition constituting the first and third layers.

Description: The present invention relates to a hose completely recyclable at the end of its working life. It is known that the flexible hoses for conveying fluids of the prior art have different structures and are of different types according to the type of fluid to be carried and to the working pressure. The prior art hoses or pipes often have a multi-layer structure having an inner zone providing the impermeability to the transported fluid, a middle reinforcing layer and an external layer for locking and protecting the middle layer. The materials employed for the external and inner layers of the prior art hoses are organic or metallorganic polymers. Those materials provide hoses having the requested flexibility properties but the hoses thus constructed do not have sufficient mechanical properties. The second layer provides the requested mechanical properties to the hose because of its structure and of the material constituting the second layer which is often made by plaiting, voluting or parceling textiles, metals or thermoplastic polymers and is arranged between the external and inner layers as described above. Particularly US4.308.895 and DE 2.419.799 disclose a hose according to the precharacterising portion of claim 1. Those prior art hoses are notoriously problematic regarding their disposal or recycling at the end of their working life. The above problems are partially attenuated when the reinforcing fiber is a textile rather than a metal because it is partially recyclable and reused, according to the type of polymer used for the substratum and/or covering. The recovery of this polymer is effected by grinding the' hoses and by separating at least the larger particles of textile originally constituting the reinforcing portion of the hose from the granular polymeric material. The thus obtained granular material, deriving from hoses having the inner and external layers made of rubber, may be reused, if suitably reground and deprived of any residual textile fiber, as a low cost filler in vulcanizable elastomeric compositions. The particulate material obtained by hoses having the inner and external layers made of polymers or thermoplastic polymer compositions may be reused for manufacturing articles of a generally large thickness. Thin articles cannot be manufactured because the recycled material has low mechanical properties due to the fibers trapped into the particulate and that cannot be eliminated by further grinding the material because of its thermoplasticity. In particular, it is not possible to reuse the material for manufacturing hoses because the textile filaments would not allow the impermeability of the hose to the conveyed fluids. A different use of the recycled material, such as injection molding, is not practically possible because the textile residues may jam the nozzles of the injectors. The aim of the present invention is to eliminate the above cited inconveniences of the prior art by providing a hose which is completely recyclable at the end of its working life Within this aim, an important object of the invention is to provide a hose having a high percentage of biodegradable material. A further object of the invention is to provide a recyclable hose which also has at least the same physical and mechanical properties of the prior art hoses and which is reliable, safe and of low cost. The above technical aim, as well as the above and other objects that will be more apparent hereinafter, are achieved by a recyclable hose according to the characterising portion of claim 1. Further characteristics and advantages of the invention will be more apparent by the following description of an embodiment of the invention, illustrated, by way of example in the enclosed drawings wherein: FIG. 1 is a perspective sectional view of a hose having four layers according to the invention; FIG. 2 is a perspective sectional view of a hose having seven layers according to the invention; FIG. 3 shows a variated embodiment of the hose according to the invention. With particular reference to the above figures, the hose according to the invention, globally designated by the reference numeral 1, has four mutually associated concentric layers. A first layer 2, inside the hose, is made for example by extrusion of a polyethylene with and MFI (Melt Flow Index) suitable to this type of arrangement and in any case, at 190° with 2.16 kg, comprised between 0.2 to 4 g/minute. A layer 3, overlaid on layer 2, is made of biodegradable polyolefin material or of thermoplastic rubber obtained by dynamic vulcanization of mixtures containing a crystalline polyolefin, of the PE or PP type or their mixtures and from polyolefin rubbers of the EPDM/EPM type. A third reinforcing layer 4 is made by plaiting, voluting or parceling layer 3 with a textile of PP fiber having a count between 5 and 9 g/denier and preferably between 5.5 and 8 g/denier and having a melting point from 110°C to 180°C and preferably from 120°C to 165°C. A covering layer 5, overlaid on layer 4 has the same composition of layer 3. According to a different embodiment, the hose according to the invention is made as described above and is however provided with layers 6 between layers 2 and 3, between layers 3 and 4 and between layers 4 and 5. Layers 6 are constituted by a thermoplastic polyolefin made functional by, for example, maleic anhydride for improving the adhesion and compatibility between the layers where this layer 6 is provided. According to a further embodiment, not shown in the drawings, the hose according to the invention has three layers, the first inner layer 2 being constituted by a thermoplastic rubber partially or completely dynamically vulcanized and based on thermoplastic polyolefins, mostly of crystalline type, preferably chosen among polyethylene and its relative copolymers and polypropylene and its relative copolymers and of polyolefin elastomers of the type EPDM/EPM or nitrile rubbers made compatible to PE or PP type mainly crystalline polyolefins and their relative copolymers. The second reinforcing layer 4 and the third covering layer 5 constituting the hose have the same characteristics of the hose made according to the above described four layer embodiment. The hose according to the invention was subjected to tests in order to prove its actual recyclability. The results were then compared with the results of analogous tests carried on hose of different types not made according to the invention. The hose subjected to the tests were: a sample 1 of the hose according to the preferred four layer embodiment of the invention, internal diameter of 13 mm and external diameter of 21 mm, constituted by 9.5% weigh/m of layer 2, 43.9% of layer 3, 3.9% of layer 4 and 42.5% of layer 5, and a sample 2 of a hose having a composition identical to that of the above describe type except that the reinforced layer was made of polyester fibers of the same count. The samples were ground, worked in a two cylinder mixer at a temperature of 190°C +/-5°C to obtain a homogeneous mass from which a 3-4 mm sheet was obtained. Sheets 1 and 2 were thus obtained from the hose samples 1 and 2. A sample 3 of hose 2, reinforced by polyester, was ground to granules, then these granules were mixed to 10 parts by weigh of a compatibiliter normally used in recycling thermoplastic materials and into a cylinder mixer; the process was continued as described above to obtain sheets 3. A sample of each sheet was stamped by compression at, 190°C +/-3°C, into a slab of 20x20x0.2 cm and its mechanical properties were then measured. A second sample of said sheets was granulated and the granules were fed into a 30 mm diameter drawbench having a Length/Diameter ratio of 20 and to a injection press. The resultant data were the following. Sample 1 Sample 1A Sample 2 Sample 3 Conformation compression injection compression compression Shore Hardness A (points) 81 82 82 85 Module at 100% Elongation (MPa) 3.8 3.9 4.7 - Ultimate Tensile Stress (MPa) 7.4 9.5 4.6 7.5 Ultimate Elongation 438 600 193 72 Slab Appearance good good streaked streaked Presence of Textile Residues no no yes yes Extrudibility excellent excellent bad bad Injection Moldability excellent excellent bad bad The results of the above described tests prove that the material constituting the hose according to the invention (samples 1 and 1A) can be completely reused and that the hose can be recycled to be used in delicate workings. The results in fact show that the Ultimate Tensile Stress and the Ultimate Elongation of Sample 2, containing the polyester fiber textile, are respectively reduce by 38% and 56% with respect of Sample 1 because of the presence of textile residues which is the cause of discontinuity in the material and possibly of permeability if the material has to be used as substratum for hoses. The percentage decrease of the properties of Sample 2 increases with respect of injection molded Sample 1A wherein the production method causes the orientation of the material. In Sample 3 the effect of the compatibiliter, constituted by a high hardness polymer, is added to the effect of the polyester textile residues and the Elongation Module at 100% is not even measurable because the recycled material breaks before reaching such limit. On the contrary, the recycled material of Sample 1 containing the polypropylene fiber textile is completely recyclable regarding its mechanical and workability properties and can be reused in the same type of original article. The main feature of the hose according to the invention is the complete absence of textile residues which allows to obtain an homogeneous material usefully and economically reusable. According to a variated embodiment, the hose is defined by a first layer 10 constituted by a partially or completely dynamically vulcanized thermoplastic rubber or by an elastomeric polyolefin. The second reinforcing layer is instead defined by a reinforcing coil 14 embedded in the first layer as shown in FIG. 3. In particular, coil 14 is constituted by a mainly crystalline thermoplastic polyolefin chosen among PE/PP or their copolymers. In order to prevent an excessive shrinkage of the material of the coil during the manufacturing of the hose, the coil may be constituted by a partially or completely dynamically vulcanized thermoplastic rubber with a high content of mainly crystalline thermoplastic polyolefin. It has been seen in practice that the hose according to the invention is particularly advantageous from the point of view of the environment because the materials can be recycled and from the economical point of view because the recycled material can be completely reused with no limitations whatsoever. Furthermore, the hoses according to the invention can float and are therefore easily retrieved if left in the sea, lakes or rivers. The possibility of manufacturing unions with thermoplastic.materials compatible with the materials constituting the hose allows to dispose of the pipings without disassembling and to recycle and reused them completely. The materials employed, as well as the dimensions, may be any according to the specific needs and the state of the art.

Claims: Recyclable hose (1) comprising a plurality of mutually associated coaxial layers, said layers comprising at least one inner layer (2) having a surface adapted to contact a fluid to be carried, at least one second reinforcing layer (4) and at least one third external layer (5) adapted to protect and lock said at least one second reinforcing layer, wherein said inner layer (2), said second reinforcing layer (4) and said third external layer (5) constituting said hose (1) are constituted by mutually completely compatible and mixable materials, characterized in that said polymer or said polymer composition constituting said at least one first layer (2) of said hose (1) is a thermoplastic polyolefin, said at least one third covering layer (5) is constituted by a polymer or polymer composition equal to the polymer or polymer composition of said at least one first layer (2), and said at least one second reinforcing layer (4) is constituted by a mainly crystalline thermoplastic polyolefin. Hose (1), according to claim 1, characterized in that said at least one second reinforcing layer (4) is constituted by textile fibers. Hose (1), according to one or more of the preceding claims, characterized in that said textile fibers are applied by plaiting, voluting or parceling on the underlying layers. Hose, (1) according to one or more of the preceding claims, characterized in that said at least one second reinforcing layer (4) is constituted by PP fibers. Hose (1), according to one or more of the preceding claims, characterized in that it comprises at least one fourth layer (3) arranged between said at least one first layer (2) and said at least one second reinforcing layer (4), said at least one fourth layer (3) being adapted to increase the thickness. Hose (1), according to one or more of the preceding claims, characterized in that said thermoplastic polyolefin constituting said at least one first layer (2) of said hose (1) is mainly crystalline. Hose (1), according to one or more of the preceding claims, characterized in that said mainly crystalline thermoplastic polyolefin constituting said at least one first layer (2) is chosen among polyethylene and its relative copolymers or among polypropylene and its relative copolymers or its lative mixtures with EPM/EPDM. Hose (1), according to one or more of the preceding claims, characterized in that said polymer or said polymer composition constituting said at least one first layer (2) of said hose (1) is constituted by a partially or completely dynamically vulcanized thermoplastic rubber. Hose (1), according to one or more of the preceding claims, characterized in that said partially or completely dynamically vulcanized thermoplastic rubber is based on mainly crystalline thermoplastic polyolefins. Hose (1), according to one or more of the preceding claims, characterized in that said partially or completely dynamically vulcanized thermoplastic rubber is based on EPDM/EPM type polyolefin elastomers or compatible nitrile rubber. Hose (1), according to one or more of the preceding claims, characterized in that said polymer or polymer composition constituting said at least one fourth layer (3) is a partially or completely dynamically vulcanized thermoplastic rubber. Hose (1), according to claim 11, characterized in that said partially or completely dynamically vulcanized thermoplastic rubber is based on mainly crystalline thermoplastic polyolefins. Hose (1), according to one or more of the preceding claims, characterized in that said thermoplastic rubber constituting said at least one fourth layer (3) is based on EPDM/EPM type polyolefin elastomers or compatible nitrile rubber. Hose (1), according to one or more of the preceding claims, characterized in that said fourth layer (3) is constituted by biodegradable thermoplastic polyolefins such as polyethylene and its copolymers containing starch. Hose (1), according to one or more of the preceding claims, characterized in that said at least one third covering layer (5) is constituted by a polymer or polymer composition equal to the polymer or polymer composition of said at least one fourth layer (3). Hose (1), according to one or more of the preceding claims, characterized in that between at least two layers constituting said hose (1), it comprises a layer constituted by a thermoplastic polyolefin functional with at least one maleic anhydride for improving the adhesion and . compatibility between the layers where it is provided. Hose (1), according to one or more of the preceding claims, characterized in that said at least one first layer (2) of said hose (1) is constituted by a mainly crystalline partially or completely dynamically vulcanized thermoplastic rubber. Hose (1), according to one or more of the preceding claims, characterized in that said at least one first layer (2) of said hose (1) is constituted by an elastomeric polyolefin. Hose (1), according to one or more of the preceding claims, characterized in that said at least one second reinforcing layer (4) comprises a coil embedded in said first layer (2), said coil being constituted by a mainly crystalline thermoplastic polyolefin chosen among PE/PP or their copolymers. Hose (1), according to one or more of the preceding claims, characterized in that said coil is constituted by a partially or completely dynamically vulcanized thermoplastic rubber with a high content of mainly crystalline thermoplastic polyolefin.

Inventors: GENNASIO GUIDO, GENNASIO, GUIDO
Applicants: TPR S P A NUCLEO IND, TPR S.P.A. NUCLEO INDUSTRIALE
Application year: 1999
Main classification: F16L11
IPC codes: F16L11, B32B1