Flexible hose of multilayer plastics material

A flexible hose of multilayer plastics material for transporting fluids, the hose comprising from the inside towards the outside: PA1 an inner layer of a polyolefin that is inert relative to water; PA1 a bonding layer having adhesive properties relative to the polyolefin and to the flexible polyvinyl chloride; PA1 a layer of flexible polyvinyl chloride; and PA1 tubular reinforcement in contact with the polyvinyl chloride.

The present invention relates to a flexible hose of multilayer plastics
 material for carrying fluids, e.g. for the purpose of being fitted in
 fixed or moving installations for distributing potable water.
 BACKGROUND OF THE INVENTION
 At present, elements for fitting in circuits for distributing potable
 water, e.g. pipes, faucets, or couplings, need to receive health standards
 approval at two levels. At a first level, the elements can be used only in
 applications where it comes into contact with the transported potable
 water for short durations only, possibly in repeated manner. In the second
 level, the element is suitable for use in any application concerned with
 transporting potable water, and in particular applications where water is
 continuously in contact with the element.
 All pipes complying with second level are rigid in structure. Thus, such
 pipes are known that are made of special rigid polyethylene,
 polypropylene, or polyvinyl chloride that are inert both chemically and
 physically relative to the potable water being transported. Such pipes are
 easy to manufacture and of low cost, so they are in widespread use in
 distribution installations. Nevertheless, the rigidity of such plastic
 material pipes puts limits on installation thereof and maintenance
 thereof.
 There thus exists a need that is not conveniently satisfied at present for
 a pipe that is easy to fit in permanent or temporary manner in an
 installation for distributing potable water.
 OBJECTS AND SUMMARY OF THE INVENTION
 To this end, the invention provides a flexible hose of multilayer plastics
 material, comprising from the inside towards the outside:
 an inner layer of a polyolefin that is inert relative to water;
 a bonding layer having adhesive properties relative to the polyolefin and
 to the flexible polyvinyl chloride;
 a layer of flexible polyvinyl chloride; and
 tubular reinforcement in contact with the polyvinyl chloride.
 A hose made in this way presents a structure that makes it suitable for
 transporting potable water, has flexibility that makes the hose easy to
 fit, and possessing relatively good mechanical qualities, in particular
 concerning bursting strength, given the pressure that is usually to be
 found in the circuits for which the hose is intended, and strength against
 external forces.
 Furthermore, it has been found that this hose presents good resistance to
 solvents, in particular at temperatures of less than about 40.degree. C.
 Furthermore, this hose also presents the property of withstanding strong
 acids and bases at temperatures of less than 40.degree. C.
 In a particular embodiment, the thicknesses of the layers lie in the
 following ranges:
 0.1 mm to 1 mm approximately for the inner layer;
 0.1 mm to 0.3 mm approximately for the bonding layer; and
 0.5 mm to 4 mm approximately for the layer of polyvinyl chloride.
 This structure represents a good compromise between flexibility and
 mechanical strength.

MORE DETAILED DESCRIPTION
 With reference to the FIGURE, the hose of the invention has an inner layer
 1 made of a polyethylene whose characteristics are compatible with
 transporting water and comply with health standards that require such a
 layer to be suitable for being continuously in contact with stagnant
 water. Specifically, the material used is inert, both physically and
 chemically, relative to the transported water so as to avoid giving rise
 to any unacceptable modification of the composition of foods or to any
 spoiling of the organoleptic properties thereof. The thickness of the
 inner layer 1 lies in the range 0.1 mm to 1 mm. The thinness of the inner
 layer makes it deformable and contributes to imparting flexibility to the
 hose. By way of example, for a hose having an inside diameter of 12 mm,
 the inner layer has thickness of about 0.5 mm and the polyethylene used is
 the polyethylene produced by Hoechst under the reference Hostalem MPE80.
 The inner layer 1 can also be made out of any other polyolefin approved
 for potable water, and in particular out of polypropylene.
 The inner layer 1 is covered in an intermediate layer 2 that bonds the
 inner layer 1 to an outer layer 3 that is made of polyvinyl chloride and
 that covers the intermediate layer 2.
 The intermediate layer 2 is made of a material that has adhesive properties
 both with polyethylene and with polyvinyl chloride. Specifically, the
 intermediate layer 2 is made from an ethylene vinyl acetate (EVA)
 copolymer which adheres to the layers 1 and 3. The copolymer used is of
 food grade. By way of example, the material used comes from Dupont de
 Nemours and is referenced Elvax 170. The thickness of the intermediate
 layer 2 lies in the range 0.1 mm to 0.3 mm, and in this case is about 0.2
 mm.
 The outer layer 3 is constituted by a first layer 3A of flexible polyvinyl
 chloride of thickness lying in the range 0.5 mm to 2 mm, and a second
 layer 3B of flexible polyvinyl chloride layer, likewise of thickness lying
 in the range 0.5 mm to 2 mm. The polyvinyl chloride used is of food grade.
 The outer layer 3 could also be made as a single piece.
 Tubular reinforcement 4 is placed in contact with the polyvinyl chloride
 between the two layers 3A and 3B of the outer layer 3. Naturally, the
 tubular reinforcement 4 could also be located between the intermediate
 layer 2 and the outer layer 3. In this case the tubular reinforcement 4 is
 based on fibers of polyethylene terephthalate (PET). It would also be
 possible to use fibers of polyamide or of polypropylene.
 The hose made in this way complies with the [French] Regulation of May 29,
 1997 relating to objects used in the distribution potable water for human
 consumption.
 Furthermore, it will be observed that this hose possesses physico-chemical
 properties that enable it to withstand solvents and strong acids and bases
 at temperatures below about 40.degree. C.
 The hose of the invention is made using the well-known technique of
 coextrusion.
 In general, the thicknesses of the various layers are determined in such a
 manner as to ensure that the hose is sufficiently flexible and strong, and
 they are adapted to the inside diameter of the hose.
 Naturally, the invention is not limited to the embodiment described, and
 variants could be made thereto without going beyond the ambit of the
 invention as defined by the claims.