Background of the invention The invention concerns a method of producing a hose pipe which is built up in a number of layers including a barrier layer of metal, said layers com- prising an innermost layer in the form of an under-hose on which the metal layer, a layer of plastic, an armouring layer and a covering layer of rubber are applied in the formation of the hose pipe.

Hose pipes of this kind are use for the transport of fluid or gaseous media of various kinds.

Depending on the demands, which are placed on the hose, it can be pro- vided with a barrier layer for the limitation or prevention of diffusion of the medium in the hose to the surroundings. This barrier can be of various con- figurations and be of different materials, preferably metal.

In addition to this there are the demands concerning strength and flexibility to ensure that the hose does not rupture, e. g. under high pressure, external influences etc., and it can also be necessary for the hose to be able to tol- erate bending, vibrations, i. e. that it can yield without any reduction in the remaining characteristics of the hose.

Where demands are made on the barrier characteristics of the hose, and herewith the metal layer, there is known a hose that is produced by the method as described in US patent no. 4,999, 903.

The metal layer consists of a relatively soft material such as aluminium, which is folded around an inner hose in its lengthways direction, so that the

side edges of the metal layer are joined in the longitudinal direction of the hose.

Hereafter, the joints are welded together to achieve a diffusion-proof bar- rier.

In order to achieve a tight connection between the inner hose and the metal tube, a calibration of the metal tube is then carried out so that its diameter is reduced for tight abutment and contact with the inner hose.

Hereafter, an armouring layer and an outer covering are applied.

However, this method is difficult to execute, since it is desirable that the calibration takes place without any noteworthy alteration in length, which could otherwise cause damage to the inner hose. Furthermore, this known hose will be relatively inflexible.

The problem with hoses produced in this way is that the adhesion between the metal layer and the plastic layers is based on a clamping-fast by cali- bration, which results in an uncertain binding and herewith a non-uniform distribution of the influences which affect the metal layer via the inner hose.

The result of this non-uniform distribution of the forces due to the non-uni- form binding between the layers is that the forces can not be distributed and herewith absorbed by the layers, but must be absorbed primarily by the layer of metal.

This means that such a hose can not be used for media under high pres- sure, the reason being that there will be a risk of damage to the metal layer, for example by metal fatigue etc.

The object of the invention It is the object of the invention to overcome these disadvantages, and ac- cording to the invention this is achieved in that the surface of the under hose is modified by means of a plasma/corona treatment, after which a layer of polymer which can be vulcanised is applied, after which the layer of metal is applied, said metal layer then being provided with a layer of poly- mer which can be vulcanised, after which the layers are heated for vulcani- sing, followed by the application of the remaining layers.

In a surprisingly simple manner, the possibility is hereby achieved of ap- plying the metal layer in such a way that it is secured directly on the under hose, and moreover that the subsequent plastic layer is in both cases se- cured directly on the metal layer by means of a vulcanising.

The complicated calibration process can thus be completely omitted, and a hitherto-unknown good binding together between the metal layer and the plastic layers is achieved, and herewith an effective distribution of the forces which would otherwise constitute a risk of damage to the metal layer.

Furthermore, it will be possible to use several different types of metals, and herewith to produce hoses with very specific barrier characteristics and with various degrees of resilience, flexibility etc.

As disclosed in claim 2, by using a chemical agent to ensure the binding together, the layers can be vulcanised to the metal layer in a simple man- ner.

As disclosed in claim 3, by providing the metal layer with corrugations, ei- ther closely together or with mutual distance between them, the hose will

easily be able to adapt to diverse degrees of bending and herewith influen- ces without deformation or weakening.

Finally, as disclosed in claim 4, it is expedient to use the hose for the trans- port of difficult media where the demands concerning non-diffusion to the surroundings must be fulfilled, or where the transport must be effected un- der full protection of the medium.

The drawing In the following, an example embodiment of the invention will be described in more detail with reference to the drawing, where fig. 1 shows a partly sectional view of a hose pipe, and fig. 2 shows a cross-section of the example embodiment according to the invention.

Description of the example embodiment In the following, an example of an embodiment of a flexible hose pipe pro- duced by the method according to the invention will be described in more detail.

The starting point for the production of the hose 1 is an under hose 2 which is shown to the left in fig. 1 and innermost in fig. 2. The object of the under hose 2 is to ensure the constancy of the medium transported in the hose 1 and to provide the metal barrier layer with protection against influences from the medium.

Where materials and dimensions are concerned, the under hose 2 is se- lected so that it can withstand the chemical influences to which it may be exposed by the media transported in the hose 1. The material dimension can, for example, be a layer thickness of from 0.1 mm to 3.0 mm.

The material will typically consist of suitable plastic such as PTFE, ETFE, PFA, FEP, PET, or an elastomer such as FKM, QM, FQM, HNBR, EAM, EACM, IIR, EPDM.

Where the hose 2 is made of fluorine-plastic such as ETFE, the surface will comprise fluorine-atoms, which will counteract a binding with the succeed- ing layer.

In order to achieve the necessary binding, the surface must be pre-treated chemically so that the surface is modified by the fluorine-atoms in the plas- tic surface being replace by radicals. This is effected by surface process- ing in the form of a plasma/corona treatment.

In this way, a chemical agent/structure will be fixed on the radicals which make binding with the succeeding layer possible. This succeeding layer can, for example, consist of the application of a dissolved silane connec- tion, which can be based on aminopropyltriethoxysilane.

Only by being heated this chemical agent/structure can be activated, utiliz- ing a vulcanisation of the layers, when use is made of a vulcanisable poly- mer as binding agent between the hose 2 and the metal layer 4. As vul- canisable polymer, use can be made of a mixture, for example based on FKM (fluorine-containing polymer, where the fluorine content can lie be- tween 50-72%).

To ensure a binding to the metal layer, here it is also necessary to apply a chemical agent to the metal layer 4, which ensures the binding to the vul- canisable polymer.

The binding between the metal layer 4 and the succeeding layer 6 is en- sured by using an elastomer containing a chemical binding promoter, which e. g. can consist of a zinc salt of methacrylic acid.

Hereafter, the metal layer 4 is treated externally so that the vulcanisable polymer can bind hereto, which can be effected by applying a dissolved silane connection such as aminopropyltriethoxysilane. There is then applied a layer of vulcanisable polymer 5 containing zinc dimethacrylate or the like, which ensures a covalent binding to the metal layer 4. The polymer 6 can be based e. g. on EACM, ACM or similar polymers.

The object of the metal foil 4 is to constitute an effective barrier against dif- fusion of the medium to the surroundings, and in this way to seal the me- dium in the hose.

This metal barrier 4 can be of stainless steel, aluminium, copper or alloys, and the thickness of the material will typically be between 30 and 300 my.

Depending on the area of application of the hose 1, the metal layer can be selected to be of smooth or corrugated configuration. Folding and possibly welding of the metal layer or by plasma application of the metal layer can preferably achieve these configurations.

Where the metal layer 4 is formed by the wrapping around of a web of foil, this can be wound in a spiral either with or without overlap. With overlap, the foil in itself will be able to form tightness by cohesion of the overlapping part of the web in connection with the vulcanising.

In the plastic layer 6 there can be laid or moulded an armouring layer 7 to ensure that the hose is able to withstand various tractive/pressure influ- ences and to be able to resist high medium pressures.

Pressures of up to 1,200 bar will be able to arise.

The armouring layer can comprise"textile"based on PET, PA, PVA or ara- mid. Use can also be made of metal mesh/wire based on brass-coated steel or stainless steel.

Finally, the hose is protected by an outermost cover layer 8 of suitable ma- terial which can correspond to that mentioned for the under hose 2. The ob- ject of the cover layer 8 is to protect the hose against physical as well as chemical external influences. The thickness of the cover layer 8 can be between 0.8 and 2.0 mm.

Finally, the hose must be suitable for mounting, i. e. be able to be provided with coupling and threaded parts with the view to the subsequent assembly and mounting of the hose.

The production of the hose 1 can be effected either in an evenly advancing process or in separate process stages.

A flexible hose according to the invention will be able to fulfil any demands, which arise regarding durability both statistically and dynamically, also non- emission of the media and noise suppression. It will therefore be suitable for the transport of difficult media such as coolants of any kind, including gaseous media, and for the transport of sensitive, volatile foodstuffs or in- gredients such as aromatics and fuel.