WO2020003089A1 - Multilayer hose for pressurized fluids transportation - Google Patents

Abstract

Multilayer hose for pressurized fluids transportation which comprises, from the interior to the exterior: an inner layer comprising a vulcanized elastomeric material; at least one reinforcing layer comprising a plurality of metal wires or textile fibers; an extruded outer layer comprising silane crosslinked polyethylene. The multilayer hose has the advantage of being a light, flexible hose suitable for use within a wide range of temperatures, such as for example from -55°C to +145°C.

Description

MULTILAYER HOSE FOR PRESSURIZED FLUIDS TRANSPORTATION

The present invention relates to a multilayer hose for pressurized fluids transportation. In particular, the present invention relates to a multilayer hose for transporting pressurized fluids, such as hydrocarbons (e.g. mineral oils, lubricants, glycols, etc.), which is preferably used in the sectors of hydraulic systems, industrial machines, handling machines, lifting machines .

It is well known that, in order to allow an adequate transport of fluids, especially when these are pressurized oily fluids or hydrocarbons, it is necessary to use a multilayer hose provided with specific structural and chemical-physical characteristics. The material that constitutes the layer of the hose in direct contact with the transported fluid must in fact be highly impermeable to oils and hydrocarbons, besides being highly resistant to the aggression by the components constituting the transported fluid. Known multilayer hoses for pressurized fluids transportation, besides having such chemical resistance must also have high mechanical performance, for example high resistance to bursting due to an increase in internal pressure, to compression and to impact. Finally, these hoses must be flexible so that they can be handled with a certain ease during both production and use and can be wound onto reels for the storage and transport thereof.

There are numerous combinations of materials proposed in the prior art for producing multilayer hoses for applications in the aforementioned fields.

For example, multilayer hoses are known comprising from the interior to the exterior: an inner layer made of elastomeric material, placed in contact with the fluid to be transported; an intermediate reinforcing layer made of metallic or textile material and an outer layer of elastomeric material.

Usually the reinforcing layer has the mechanical function of counteracting the pressure exerted by the pressurized fluid transported, thus preventing the bursting of the hose, while the inner layer in elastomeric material has the characteristics of being impermeable and resistant to the aggression of the transported fluids. The outer layer, on the other hand, acts as a protective layer to the inner layers.

Also known are the so-called hybrid multilayer hoses comprising an inner layer of elastomeric material, an intermediate reinforcing layer made of metallic or textile material and an outer layer made of thermoplastic material .

An example of these hybrid multilayer hoses is described in EP 2290278, which describes a multilayer hose comprising an inner layer made of elastomeric material, one or more intermediate reinforcing braided or spiralized layers made of metallic or textile material and an outer layer made of thermoplastic material, such as polyurethane.

The temperature range within which it is possible to use a multilayer hose mainly depends on the material with which the inner and outer layers are made. In fact each material, whether elastomeric or thermoplastic, has its own temperature range within which its performance remains constant. At temperatures outside the aforementioned range the material can degrade, for example by melting, thus making its use at those temperatures inadequate.

Depending on the temperatures within which the hose is to be used, it is therefore necessary to choose a particular combination of materials for the inner and outer layers, so as to make the hose suitable for use in those specific temperatures.

For example, a hybrid multilayer hose comprising an inner elastomeric layer and an outer polyurethane layer has the limitation that it cannot be used at relatively high temperatures, for example above about 80 °C, since beyond that temperature the polyurethane begins to deteriorate .

In general, hoses whose performance is correctly maintained at low temperatures have the disadvantage of losing the aforementioned performance when the temperature rises and, conversely, hoses that operate correctly at high temperatures have poor performance at low temperatures. This limits the choice of the type of hose to be installed to the temperature range of use and imposes the user to install hoses with different structures and compositions for different temperature ranges of use.

Instead, it would be desirable to have multilayer hoses available capable of being used indifferently at low or high temperatures, i.e. in a wider temperature range than that of the hoses of the prior art.

The Applicant has therefore posed the problem of developing a multilayer hose for transporting pressurized fluids that is suitable for use in a wide range of temperatures, for example from -60°C to +150°C.

The Applicant has now found that this problem, and others which will be better explained below, can be solved by a hybrid multilayer hose in which the inner layer is made of elastomeric material and the outer layer is composed of a polymeric material comprising silane crosslinked polyethylene; at least one intermediate reinforcing layer comprising metal wires or textile fibers is interposed between the two layers.

In fact, it has been found that the use of a polymeric material comprising silane crosslinked polyethylene as the outer layer allows to obtain hoses usable in a wider range of temperatures. The hoses also maintain high flexibility and are significantly lighter than the hoses of the prior art, in particular than hoses having inner and outer layers of elastomeric material, with the same required performance. In fact, crosslinked polyethylene provides adequate mechanical and thermal resistance despite being used in the form of a thin layer. Furthermore, by crosslinking polyethylene by means of the "silane" technique, the production process is easy and low-cost to implement.

According to a first aspect, the present invention therefore relates to a multilayer hose for pressurized fluids transportation which comprises, from the interior to the exterior:

- an inner layer comprising a vulcanized elastomeric material;

- at least one reinforcing layer comprising a plurality of metal wires and/or textile fibers;

- an extruded outer layer comprising silane crosslinked polyethylene.

According to a second aspect, the present invention relates to the use of the aforesaid multilayer hose for transporting a pressurized fluid. Within the scope of the present description and the appended claims, "pressurized" fluids are meant as fluids circulating in a hose at a pressure in the range of 20 - 1300 bar.

Preferably, the pressurized fluids transported are selected from: hydrocarbons, mineral oils, lubricants, glycols, water and similar fluids.

The elastomeric material forming the inner layer can be chosen without particular limitations among the elastomeric materials commonly used to make the multilayer hoses of the prior art. The elastomeric material can be a natural rubber or a vulcanizable synthetic rubber, such as for example nitrile rubber, styrene-butadiene rubber (SBR), butadiene-acrylonitrile copolymers (NBR) , chlorobutadiene polymers (neoprene®) . More preferably, the elastomeric material is a butadiene-acrylonitrile copolymer .

The elastomeric material forming the inner layer is in a vulcanized form.

The inner layer delimits, internally with respect to the hose, a cavity for pressurized fluids transportation. For the purpose of the present description, by cavity it is meant the lumen or channel of the hose available for the passage of the transported fluid. Preferably, the diameter of this cavity, namely the diameter of its cross-section, is within the range from 3/16 inch to 2 inches. The inner layer is therefore in direct contact with the transported fluid, namely it is the innermost layer of the hose.

The elastomeric material preferably has a hardness value within the range from 60 to 95 Shore A (UNI EN ISO The elastomeric material preferably has a breaking load value within the range from 5 to 30 MPa (UNI 6065) .

The elastomeric material preferably has an elongation at break value within the range from 100 to 300% (UNI 6065) .

The elastomeric material preferably has a modulus value 100% within the range from 1.0 to 15.0 MPa (UNI 6065) .

In accordance with one embodiment of the present invention, the multilayer hose comprises one or more reinforcing layers (or sheaths), each comprising metal wires or textile fibers. The metal wires are preferably braided or spiralized. According to another embodiment of the invention, the textile fibers are preferably braided or spiralized.

Preferably, the metallic fibers are made of iron, while the textile fibers are preferably selected from: aramid fibers, nylon fibers, polyvinyl alcohol fibers, polyester fibers and combinations thereof.

The at least one reinforcing layer surrounding the inner layer is arranged to increase the mechanical strength of the multilayer hose; in particular, the at least one reinforcing layer is chosen so as to allow the hose to meet the burst strength requirements established by the specific industry standards.

The reinforcing layer can comprise one or more of the following elements: a sheath of possibly braided or spiralized steel wires or textile fibers. The reinforcing layer can also comprise several braided or spiralized sheaths, possibly superimposed on one another and formed for example by braided metallic wires or textile fibers. In this case, between two successive sheaths a thin layer of natural or synthetic rubber is preferably interposed, referred to in jargon as a "foil", and having the purpose of increasing the adhesion of the two or more sheaths .

Preferably the reinforcing layer is able to adhere to the inner and outer layers, allowing the layers to be mechanically fixed and avoid reciprocal sliding.

Advantageously, the reinforcing layer and the possible sheaths can be impregnated by the elastomeric material of the inner layer and/or by the polyethylene of the outer layer, for example following the manufacturing process of the multilayer hose by extrusion. This further improves the adhesion of the various layers to each other.

The outer layer surrounding the at least one reinforcing layer of the multilayer hose according to the present invention is made of a material comprising silane crosslinked polyethylene.

The polyethylene which can be used for the purposes of the present invention preferably has a hardness value within the range from 60 to 95 Shore A (UNI EN ISO 868) .

The polyethylene preferably has a breaking load value greater than 5, more preferably within the range from 5 to 30 MPa (ISO 527-2) .

The polyethylene preferably has an elongation at break value greater than 400%, more preferably within the range from 400% to 800% (ISO 527-2) .

The polyethylene preferably has a 100% modulus value within the range from 1.0 to 15.0 MPa (ISO 527-2) .

In accordance with a preferred embodiment, the outer layer of the silane crosslinked polyethylene hose advantageously has a thickness within the range from 0.2 to 1.5 mm, even more preferably it has a thickness within the range from 0.3 to 1.0 mm. This thickness of the crosslinked polyethylene layer gives the hose adequate mechanical and thermal resistance, without making the hose too stiff, which therefore maintains adequate flexibility, or significantly increasing its weight.

The thickness of the layers forming the multilayer hose according to the present invention can be measured by means of a calliper.

In particular, the multilayer hoses according to the present invention can be used continuously at temperatures in a wide range of values, for example within the range from -55°C to +145°C.

For the purposes of the present description and the appended claims, the term "continuously" means that the hose can operate indefinitely and continuously at the aforementioned temperatures. Moreover, when used for a short period of time, the multilayer hose can also be used at a lower temperature, such as for example at -60°C, or at a higher temperature, such as for example at +150°C.

The characteristic of the outer layer having a thickness within the range from 0.2 to 1.5 mm also allows the weight per unit of length of the multilayer hose to be reduced with respect to the multilayer hoses of the known art. The weight reduction advantageously makes the hose of the invention easy to handle.

The multilayer hose according to the present invention can be made with the devices and techniques known to the person skilled in the art.

In accordance with a further aspect of the present invention, the multilayer hose is preferably produced with a process that comprises the steps of:

a) extruding an annular inner layer of elastomeric material ;

b) applying on said annular inner layer at least one reinforcing layer comprising metal wires and/or textile fibers;

c) subjecting said annular inner layer and said at least one reinforcing layer to vulcanization in order to vulcanize said elastomeric material;

d) extruding an annular outer layer comprising at least one polyethylene grafted with silanes on said reinforcing layer;

e) curing said polyethylene grafted with silanes in order to obtain the multilayer hose.

Preferably, the vulcanization is carried out in an autoclave in the presence of steam.

The silane crosslinking of the polyethylene can be carried out with the processes known to the person skilled in the art, preferably with the process commonly called Sioplast®. In accordance with the Sioplast® process, a polyethylene polymer grafted with a vinylsilane compound (e.g. vinyltrimethoxysilane ) , optionally pre-mixed with at least one hydrolysis catalyst and other additives (e.g. pigments, plasticizers, etc.), is extruded on the reinforcing layer to form the outer layer. The crosslinking of the polyethylene can take place in environmental conditions. Preferably, the crosslinking can be accelerated by immersing the hose comprising the polyethylene layer in hot water (e.g. 60-95°C).

The polyethylene grafted with vinylsilane compounds can be prepared according to the prior art, for example by treating the polyethylene with an alkoxyvinylsilane compound in a mixing unit (e.g. twin-screw extruder or co-kneader), at a temperature for example of 50 - 150°C, in the presence of a peroxidic compound capable of promoting the anchoring of the alkoxyvinylsilane groups to the polyethylene chains (radical initiator) .

The production process according to the present invention has the advantage to allow the production of a multilayer hose with a particularly favourable balance between performance and production costs, in particular with respect to the processes that involve the crosslinking with peroxides of thermoplastic polymeric materials. In fact, these latter processes require expensive systems and the strict control of operating conditions, in particular of the extrusion temperature, so as to avoid triggering the decomposition of the peroxides and therefore the beginning of the crosslinking .

A further aspect of the present invention relates to the use of the multilayer hose, as previously described, for transporting a pressurized fluid, preferably at a temperature within the range from -60°C to +150 °C .

Claims

1. Multilayer hose for pressurized fluids transportation which comprises, from the interior to the exterior :

- an inner layer comprising a vulcanized elastomeric material;

- at least one reinforcing layer comprising a plurality of metal wires and/or textile fibers;

- an extruded outer layer comprising silane crosslinked polyethylene.

2. Hose according to claim 1, wherein the elastomeric material is selected from: natural rubber, nitrile rubber, styrene-butadiene rubber, butadiene- acrylonitrile copolymer, chlorobutadiene polymers.

3. Hose according to claim 2, wherein the elastomeric material is a butadiene-acrylonitrile copolymer .

4. Hose according to any one of the preceding claims, wherein the metal wires and/or the textile fibers are braided or spiralized.

5. Hose according to any one of the preceding claims, wherein the metal wires are steel wires.

6. Hose according to any one of claims from 1 to 4, wherein the textile fibers are selected from: aramid fibers, nylon fibers, polyvinyl alcohol fibers, polyester fibers and combinations thereof.

7. Hose according to any one of the preceding claims, wherein the outer layer has a thickness within the range from 0.2 to 1.5 mm.

8. Hose according to any one of the preceding claims, wherein the inner layer delimits, internally with respect to the hose, a cavity for the transportation of pressurized fluids having a diameter within the range from 3/16 inch to 2 inches.

9. Process to produce a multilayer hose according to claim 1 comprising the steps of:

a) extruding an annular inner layer of elastomeric material ;

b) applying on said annular inner layer at least one reinforcing layer comprising metal wires and/or textile fibers;

c) subjecting said annular inner layer and said at least one reinforcing layer to vulcanization in order to vulcanize said elastomeric material;

d) extruding an annular outer layer comprising at least one polyethylene grafted with silanes on said reinforcing layer;

e) curing said polyethylene grafted with silanes in order to obtain said multilayer hose.

10. Use of the multilayer hose according to claim 1 for the transportation of a pressurized fluid.

11. Use according to claim 10 at a temperature within the range from -60°C to +150°C.