LAYERED FABRIC

Abstract: Layered fabric (5), substantially liquid impervious, comprising a filamentary substrate layer (3), and outer plastics layer (4) being preferably extrusion melt coated low density polyethylene (LDPE) and a separately extruded inner plastics layer (1) preferably bonded to said filamentary layer by an extrusion melt coat of plastics material. The layered fabric can be seamed to make low cost, lightweight collapsible hose and other substantially impervious fluid containment vessels such as tank liners, having improved damage resistance.

Description: LAYERED FABRIC BACKGROUND This invention relates to a layered fabric which is substantially impervious and is thus useful as large diameter collapsible hose, and as a containment vessel including a liner for water storage and reticulation equipment,for example. The layered fabric is particularly useful in applications as cited above in which a need exists to form leak tight joins or seams in such hoses or liners. The invention particularly relates to a layered fabric comprising a filamentary layer providing an essentially reinforcing contribution to the fabric in conjunction with at least two other layers contributing in combination an impervious property. Additional layers can be included to provide further protection in an outdoor rural environment, for example. The above described layered fabric is exceptionally advantageous when formed into collapsible hose of typical diameter of 250 mm when made from a composite layered fabric of flexible synthetic plastics. - Using a laminate enables the highly economical manufacture of such hose having the advantages of low mass per unit length in relationship to its diameter and its carrying capacity, while at the same time displaying exceptional damage, overpressure, puncture and weather resistance. Hoses of this general type are known and are usefully employed for example in rural agriculture, flood mitigation and civil engineering site de-watering. The fluidised conveyance of particulate material through such hoses is also practised. -Known hoses suffer from certain disadvantages; one type made from a single layer of polyolefin film suffers in that the nominally 250 mm diameter hose is only able to withstand an internal pressure of about 20 kPa and has very poor tear, abrasion, puncture and weather resistance. Another known type is made from a woven polyester fabric coated with an extrusion melt coated layer of polyvinyl chloride on each side. Although this type has satisfactory resistance to the rigours of use it is very heavy to handle. Also it is of high cost due to the high material costs as well as the slow production rate obtaining when welding the longitudinal seam. A hose made from the layered fabric of the present invention substantially overcomes, or ameliorates, the limitations of such earlier types of hose construction because the new and useful layered fabric has an unexpectedly useful balance of properties between high performance and low cost. SUMMARY According to a first aspect of the present invention there is provided a layered fabric comprising a substrate formed from filamentary material, an outer layer of plastics material covering one surface of said substrate and an inner layer of separately extruded plastics material abutting the opposite surface of said substrate, said layers being secured over at least part of their surface areas to said substrate to form a composite substantially impervious layered fabric. According to a second aspect of the invention there is provided a method of forming a layered fabric a*-... 1 comprising the steps of:- covering one side of a substrate formed from filamentary material with an outer layer of plastics - material, abutting the other side of said substrate with . 5 an inner layer comprising a separately extruded plastics material and securing said layers to said substrate to form a composite substantially impervious layer. According to a third aspect of the invention there is provided a containment vessel made from the 10 fabric according to the first aspect of the invention. According to a fourth aspect of the invention there is provided a method of making a containment vessel from the layered fabric according to the first aspect of the invention. 15 A particularly significant embodiment of the third aspect of the invention is one in which the liquid containment vessel is longitudinally seamed, collapsible hose. A particularly advantageous and significant 20 embodiment of the first aspect of the invention is the layered fabric having the filamentary layer comprising a flexible web or strip of indefinite length composed of woven tapes of stretched polyolefin being warp tapes extending lengthways along the web and weft tapes * 25 extending transversely across the web. In a preferred _ and important embodiment the woven polyolefin layer is a substrate for a layer of low density polyolefin film on either side. In a most preferred version the two outer layers are of substantially equal width to that of the 30 filamentary layer and are adhesively bonded to the woven layer over their full area of mutual contact. The preferred bonding adhesive is an extruded melt coat of a substantially polyolefin composition such as low density polyethylene (LDPE). Some embodiments of the present invention will be described with reference to the accompanying drawings in which:- DESCRIPTION OF THE DRAWINGS Fig 1 is a transverse cross section of the longitudinal seam portion of a hose made from the laminate of a first embodiment, Fig 2 is a similar cross section of a hose made from the fabric of a second embodiment, and Fig 3 is a similar cross section of a hose according to a third embodiment. DETAILED D±& &l PTION In Figure 1, the fabric of the first embodiment of the present invention is shown in the manner in which it is most economically and conveniently formed into a hose 5 having a lap or overlap type seam which extends longitudinally. The layer forming the inside of the hose 5 as partly depicted in Fig 1 is a separately extruded layer of low density polyethylene (LDPE). This is referred to as the inner layer. The next adjacent layer 2 is an extrusion melt coated layer of LDPE which joins the inner layer 1 to the filamentary layer 3, in this case woven from stretched tapes of high density polyethylene. The other (outer) surface of the filamentary layer 3 is coated with an extrusion melt coat 4 of LDPE, which preferably contains additives capable of imparting resistance to abrasion and/or ultra-violet radiation. Fig 2 shows a second embodiment of the hose in which the inner layer 5 overhangs the remainder of the multi-layered fabric to enable a seam to be fabricated in which the inner layer 1 of LDPE is enabled to be seamed in an overlap type seam as shown. Fig 3 shows a third embodiment of the hose 5 in which the inner layer 1 is incorporated in the seam region only. The inner layer 1 can be extended in either direction to sandwich the internal and external overlap of the seam region. That is, the layer 1 has an S-shaped configuration (not illustrated) which mirrors the U-shaped configuration of Fig 2. EXAMPLE 1. A laminated structure was manufactured to the following specification:- Layer, Material Nominal thickness as numbered or mass per unit per Figure 1 area 1. Separately Blend of LDPE 50 micrometres extruded film and linear LDPE or inner layer . 2 . Melt extruded LDPE 40 to 50 micro¬ adhesive layer metres 3. Filamentary Stretched tapes of 160 grams per layer . HDPE woven as warp square metre and we ft . 4. Outer layer - LDPE 40 to 50 micro¬ melt extruded with metres UV and abrasion resi stant additives . The layered fabric was formed into a very long hose of 250 mm diameter and wall thickness approximately 0.3 mm by overlapping opposing edges of the layered fabric by 45 mm and then using heat and pressure to form a seam, by the hot air welding method in this case. At least equally satisfactory seams can be formed by ultrasonically welded or adhesive bonding methods. The resultant hose was tested by pumping water through it at a steady head of 60 kPa with occasional overpressure transients as high as 300 kPa. The hose remained substantially leaktight and remained so over the duration of the test (several hours) despite being run over several times (while water filled) by a heavy loader type vehicle fitted with tractor type tyres. The performance of this hose was regarded as remarkable in view of its low mass of 180 grams per lineal metre. Prior art type hoses without a filamentary layer failed under considerably less arduous service and those of the polyester fabric type coated with PVC only displayed comparable performance despite being approximately three times the weight and taking three times as long to seam weld as the hose as encompassed by this example. Other hoses where an inner LDPE layer was not separately extruded but was a melt coat of the same material leaked profusely under test from pinholes formed partly as a result of circumferential stretching of the hose under the pressure head obtaining during the test. The leakage was particularly high at the welded seam region. Variations include a variety of generally similar materials for the filamentary layer; as well as polyolefin materials, polyester, nylon and other synthetic or natural fibres can be included as part or all of the filamentary layer which can include woven or non-woven constructions. The layers 2 and 4 of LDPE, extrusion coated in a molten form onto the filamentary layer 3, can instead be an adhesive composition preferably in a vehicle enabling application at room temperatures. In such a case the inner and outer layers can both be separately extruded film of the type of the inner layer. Also, at least the innermost adhesive layer can be omitted, or used only in the seam region or only in discontinuous areas of mutual contact between the adjacent layers. The several layers can be formulated or selected with specific desired properties, including, for example, UV and abrasion resistance, fire retardance, acceptability for contact with potable water, and colour for identification purposes. The number of seams in a hose or tube is not limited to one in number and the seam configuration is not limited to the lap (ie overlap) type as illustrated but can be the fin type. Rather than forming the hose or tube by forming a longitudinal seam it can be formed by spirally winding and seaming. It will be apparent that a most advantageous embodiment of a hose according to the present invention is one in which a multi-layer web or strip of indefinite length is formed into a hose by heat and pressure welding a longitudinal lap seam. The hose is composed of an internal layer of separately extruded LDPE, preferably bonded to a polyolefin layer which in turn is coated externally by a melt extruded layer of LDPE. This outer layer can include additives to enhance ultra-violet stability of the hose when exposed to direct sunlight and/ or additives to impart abrasion resistance . An alternative structure is one in which the above mentioned separately extruded internal layer of LDPE occupies substantially only the seam region (as in Fig 3) . USES AND ADVANTAGES The layered fabric disclosed shows particular advantage when constructed into a layflat, collapsible hose, of diameter typically 100 mm or greater where advantages over known prior art hoses of similar types are as follows: 1. Excellent abrasion, puncture, tear, pressure and weather resistance when compared to known single layer hoses of the same general class used for similar purposes, and 2. Highly economical manufacture with approximately three times faster rates of seam formation than known prior art ulti- layer hoses of the same general type. As well, the hose is of low mass, has relatively low material costs and can be more easily fitted with lateral outflow fittings than known multi-layer types. Although the preferred embodiment is a hose, the above described fabric can be made into other containment vessels such as tank liners, dam liners, and the like. The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.

Claims: WHAT IS CLAIMED IS: 1. A layered fabric(5) comprising a substrate(3) formed from filamentary material, an outer layer(4) of plastics material covering one surface of said substrate and an inner layer(l) of separately extruded plastics material abutting the opposite surface of said substrate, said layers being secured over at least part of their surface areas to said substrate to form a composite substantially impervious layered fabric. 2. A layered fabric as claimed in claim 1 wherein said substrate is selected from the group consisting of woven and non-woven fabrics. 3. A layered fabric as claimed in claim 2 wherein said substrate is formed from filamentary plastics material. 4. A layered fabric as claimed in claim 3 wherein said filamentary plastics material is polyolefin. 5. A layered fabric as claimed in any one of claims 1 to 4 wherein the inner layer is joined to said substrate over substantially all its area. 6. A layered fabric as claimed in claim 5 wherein the inner layer is joined to the substrate by a layer of hot melt material(2). 7. A layered fabric as claimed in claim 6 wherein the material comprising the hot melt material is the material of the outer layer. 8. A layered fabric as claimed in claim 7 wherein the material comprising the inner layer is low density polyethylene. 9. A layered fabric as claimed in any one of claims 1 to 4 wherein said outer layer is an extrusion melt coat on said substrate. 10. A layered fabric as .claimed in claim 9 wherein the outer layer is low density polyethylene. 11. A method of forming a layered fabric(5) comprising the steps of: covering one side of a substrate formed from filamentary material with an outer layer(4) of plastics material abutting the other side of said substrate with an inner layer(1) comprising a separately extruded plastics material, and securing said layers to said substrate to form a composite substantially impervious layered fabric. 12. A method of forming a layered fabric as claimed in claim 11 wherein said substrate is selected from the group consisting of woven and non-woven fabrics. 13. A method of forming a layered fabric as claimed in claim 12 wherein said substrate is formed from filamentary plastics material. 14. A method of forming a layered fabric as claimed in claim 13 wherein said plastics material is polyolefin. 15. A method of forming a layered fabric as claimed in any one of claims 11 to 14 wherein the inner layer is joined to said substrate over substantially all its area. 16. A method of forming a layered fabric as claimed in claim 15 wherein the inner layer is joined to the substrate by using a layer of hot melt material(2) . 17. A method of forming a layered fabric as claimed in claim 16 wherin the joining of the inner layer to the substrate is carried out using the material of the outer layer. 18. A method of forming a layered fabric as claimed in claim 17 wherein the material comprising the inner layer is low density polyethylene. 19. A method of forming a layered fabric as claimed in any one of claims 11 to 14 wherein said plastics material of said outer layer is extrusion melt coated on said substrate to cover same. 20. A method of forming a layered fabric as claimed in claim 19 wherein the outer layer is low density polyethyelene. 21. A containment vessel formed from the layered fabric of any one of claims 1 to 4. 22. A vessel as claimed in claim 21 when ha ing one or more seams . 23. A vessel as claimed in claim 22 having a seam selected from the group comprising hot air welded, ultrasonically welded and adhesively bonded. 24. A vessel as claimed in claim 23 having a seam selected from the group consisting of overlap and fin configurations. 25. A vessel as claimed in claim 24 wherein the vessel is a collapsible hose. 26. A vessel as claimed in any one of claims 21 to 25 wherein the inner layer of the layered fabric is bonded to the substrate in the seam region only. 27. A vessel as claimed in any one of claims 21 to 25 wherein an additional layer of inner layer material(l) is incorporated as part of the seam. 28. A vessel as claimed in any one of claims 21 to 25 wherein one or more layers of inner layer material is/are used in the seam region only. 29. A method of making a containment vessel from the fabric of any one of claims 1 to 4 wherein an area of said fabric is formed into a generally enclosed configur tion. 30. A method of making a vessel as claimed in claim 29 including the step of forming one or more seams. 31. A method of making a vessel as claimed in claim 30 wherein said seam forming is carried out using a technique selected from the group consisting of hot air welding, ultrasonic welding and adhesive bonding. 32. A method of making a vessel as claimed in claim 31 wherein said seam forming is carried out using a seam configuration selected from the group consisting of overlap and fin seams. 33. A method of making a vessel as claimed in claim 32 wherein the vessel is a collapsible hose. 34. A method of making a vessel as claimed in any one of claims 30 to 33 wherein the inner layer of the layered fabric is bonded to the substrate in the seam region only. 35. A method of making a vessel as claimed in any one of claims 30 to 33 wherein an additional layer of inner layer material is incorporated as part of the seam. 36. A method of making a vessel as claimed in any one of claims 30 to 33 wherein one or more layers of inner layer material is used in the seam region only.

Inventors: DELLER PAUL NICHOLAS, TERRY PETER RICHARDS, DELLER, PAUL, NICHOLAS, TERRY, PETER, RICHARDS
Applicants: RHEEM AUSTRALIA PTY LTD, RHEEM AUSTRALIA LIMITED
Application year: 1985
Main classification: B32B27
IPC codes: B29C65, B32B27, B65D65